240 area code
The 240 area code serves parts of Maryland, including Germantown. Established as an overlay to the 301 area code, it was introduced to address the growing demand for telephone numbers in the region. The area code plays a crucial role in providing telecommunication services to residents, businesses, and organizations in the Germantown area, contributing to the overall connectivity and communication infrastructure of the state.
| State | Maryland |
| Major City | Germantown |
| Timezone | Eastern Time Zone (ET) |
What time zone is area code 240?
Area code 240 is located in the Eastern Time Zone (ET) in the United States. This time zone is four hours behind Coordinated Universal Time (UTC-4). As part of the Eastern Time Zone, area code 240 observes standard time and daylight saving time, aligning with the practices of the broader region. The time zone is utilized to maintain consistent and synchronized timekeeping across the geographic areas covered by the 240 area code, ensuring coordinated scheduling and communication within this region.
Note that the start and end dates of daylight saving time can change
History
The 240 area code, introduced in 1997, is a relatively recent addition to Maryland's telecommunications landscape. It was implemented to provide additional numbering resources as an overlay to the existing 301 area code. This overlay allowed new phone numbers to be assigned without requiring geographic relocation or disruption for existing residents and businesses. The 240 area code has since become an integral part of Maryland's telecommunications infrastructure, facilitating the growing demand for telecommunication services in the state and contributing to the efficient communication network that supports local communities, businesses, and government entities.
Nearby Areacodes of 240
This table provides a quick overview of all area codes, their locations, and some historical context for each.
| Area Code | Location | History and Details |
|---|---|---|
| 202 | District of Columbia | The 202 area code serves the District of Columbia, encompassing the nation's capital, Washington, D.C. Established in 1947, it has played a pivotal role in connecting government offices, residents, and businesses in the heart of the United States. |
| 223/717 | Lancaster, PA | The 223/717 area code covers Lancaster, PA, and nearby areas. Serving as an overlay to the 717 area code, it ensures ample numbering resources for effective communication in this region. |
| 240/301 | Germantown, MD | The 240/301 area code serves Germantown, MD, and is an overlay introduced to address the growing demand for telephone numbers in the region. It plays a crucial role in the telecommunications infrastructure of Maryland. |
| 304/681 | West Virginia | The 304/681 area code covers the state of West Virginia. Established to meet the increasing demand for telephone services, it serves as a key component of the telecommunications network in the region. |
| 410/443/667 | Baltimore, MD | The 410/443/667 area code covers Baltimore, MD, and surrounding areas. It has a rich history of providing essential telecommunication services to residents, businesses, and institutions in this vibrant city. |
| 434 | Lynchburg, VA | The 434 area code serves Lynchburg, VA, and the surrounding region. Established to meet the telecommunication needs of the area, it has become an integral part of connecting communities in central Virginia. |
| 484/610 | Allentown, PA | The 484/610 area code covers Allentown, PA, and nearby areas. Serving as an overlay to the 610 area code, it has played a crucial role in meeting the growing demand for telephone services in this region. |
| 540 | Roanoke, VA | The 540 area code serves Roanoke, VA, and the surrounding areas. Established to accommodate the increasing demand for telephone services, it plays a key role in the telecommunications infrastructure of southwestern Virginia. |
| 571/703 | Arlington, VA | The 571/703 area code covers Arlington, VA, and neighboring areas. It has a history of providing essential telecommunication services to this region, contributing to the connectivity of the Washington metropolitan area. |
| 724 | New Castle, PA | The 724 area code serves New Castle, PA, and nearby areas. Established to meet the telecommunication needs of the region, it has become an integral part of connecting communities in western Pennsylvania. |
| 757 | Virginia Beach, VA | The 757 area code covers Virginia Beach, VA, and surrounding areas. It has a history of providing essential telecommunication services to residents, businesses, and institutions in this coastal city. |
| 304/681 | West Virginia | The 304/681 area code covers West Virginia, providing telephone services to residents and businesses. It has played a significant role in connecting communities and supporting communication infrastructure in the state. |
| 410/443/667 | Baltimore, MD | The 410/443/667 area code serves Baltimore, MD, and the surrounding areas. Established to meet the growing demand for telephone numbers, it is an essential component of the telecommunications network in central Maryland. |
| 434 | Lynchburg, VA | The 434 area code covers Lynchburg, VA, providing telecommunication services to the local community. It has been instrumental in meeting the communication needs of residents and businesses in the region. |
| 484/610 | Allentown, PA | The 484/610 area code serves Allentown, PA, and nearby areas. Established to accommodate the demand for telephone numbers, it contributes significantly to the telecommunication infrastructure in eastern Pennsylvania. |
| 540 | Roanoke, VA | The 540 area code covers Roanoke, VA, and surrounding regions. It plays a crucial role in providing telecommunication services to residents and businesses, contributing to the connectivity of southwestern Virginia. |
| 571/703 | Arlington, VA | The 571/703 area code serves Arlington, VA, and the neighboring areas. Established to meet the increasing demand for telephone services, it is an essential part of the telecommunication network in northern Virginia. |
| 724 | New Castle, PA | The 724 area code covers New Castle, PA, and surrounding regions. It has been instrumental in providing telecommunication services to the local community, supporting connectivity in western Pennsylvania. |
| 757 | Virginia Beach, VA | The 757 area code serves Virginia Beach, VA, and nearby areas. Established to fulfill the growing communication needs, it is a key component of the telecommunication infrastructure in southeastern Virginia. |
| 804 | Richmond, VA | The 804 area code covers Richmond, VA, and the surrounding areas. Established to meet the increasing demand for telephone services, it plays a vital role in the telecommunications infrastructure of central Virginia. |
| 814 | Erie, PA | The 814 area code serves Erie, PA, and nearby regions. It has been a longstanding area code, playing a crucial role in telecommunications in northwestern Pennsylvania. |
| 878 | Pittsburgh, PA | The 878 area code covers Pittsburgh, PA, and surrounding areas. Established to meet the growing demand for telephone numbers, it is an integral part of the telecommunication infrastructure in southwestern Pennsylvania. |
Counties in Area Code 240
Area code 240 covers a total of 11 counties in the state of Maryland. These counties include a diverse range of landscapes and communities, from the eastern plains to the western mountains.
| County | Total Population | % of 240 | % of County |
|---|---|---|---|
| Montgomery, MD | 971,777 | 11% | 100% |
| Prince George's, MD | 863,420 | 10% | 100% |
| Frederick, MD | 233,385 | 14% | 96% |
| Washington, MD | 147,430 | 10% | 100% |
| Charles, MD | 146,551 | 13% | 100% |
| St. Mary's, MD | 105,151 | 16% | 100% |
| Allegany, MD | 75,087 | 9% | 100% |
| Howard, MD | 287,085 | 1% | 24% |
| Anne Arundel, MD | 537,656 | 1% | 7% |
| Garrett, MD | 30,097 | 14% | 100% |
| Calvert, MD | 88,737 | 1% | 8% |
Cities in Area Code 240
Here are the some of the major cities and towns in Kentucky covered by area code 240 include Cheyenne, Casper, Laramie, Gillette, Rock Springs, Sheridan, Jackson, Cody, and Evanston, among others. There are many more smaller towns and communities within this area code as well.
| County | Total Population | % of 240 | % of County |
|---|---|---|---|
| Montgomery, MD | 971,777 | 11% | 100% |
| Prince George's, MD | 863,420 | 10% | 100% |
| Frederick, MD | 233,385 | 14% | 96% |
| Washington, MD | 147,430 | 10% | 100% |
| Charles, MD | 146,551 | 13% | 100% |
| St. Mary's, MD | 105,151 | 16% | 100% |
| Allegany, MD | 75,087 | 9% | 100% |
| Howard, MD | 287,085 | 1% | 24% |
| Anne Arundel, MD | 537,656 | 1% | 7% |
| Garrett, MD | 30,097 | 14% | 100% |
| Calvert, MD | 88,737 | 1% | 8% |
| Germantown, MD | 86,395 | 0% | 100% |
| Silver Spring, MD | 71,452 | 0% | 100% |
| Waldorf, MD | 67,752 | 1% | 100% |
| Frederick, MD | 65,239 | 0% | 100% |
| Rockville, MD | 61,209 | 0% | 100% |
| Bethesda, MD | 60,858 | 0% | 100% |
| Gaithersburg, MD | 59,933 | 0% | 100% |
| Bowie, MD | 54,727 | 0% | 100% |
| Aspen Hill, MD | 48,759 | 0% | 100% |
| Wheaton, MD | 48,284 | 0% | 100% |
| Potomac, MD | 44,965 | 1% | 100% |
| Germantown, MD | 86,395 | 0% | 100% |
| Silver Spring, MD | 71,452 | 0% | 100% |
| North Bethesda, MD | 43,828 | 0% | 100% |
| Hagerstown, MD | 39,662 | 0% | 100% |
| Clinton, MD | 35,970 | 1% | 100% |
| Montgomery Village, MD | 32,032 | 0% | 100% |
| College Park, MD | 30,413 | 0% | 100% |
| South Laurel, MD | 26,112 | 0% | 100% |
| Suitland, MD | 25,825 | 0% | 100% |
| Laurel, MD | 25,115 | 0% | 100% |
| North Potomac, MD | 24,410 | 0% | 100% |
| Scaggsville, MD | 24,333 | 0% | 100% |
| Fort Washington, MD | 23,717 | 0% | 100% |
| Fairland, MD | 23,681 | 0% | 100% |
| Landover, MD | 23,078 | 0% | 100% |
| Montgomery, MD | 971,777 | 11% | 100% |
| Prince George's, MD | 863,420 | 10% | 100% |
| Frederick, MD | 233,385 | 14% | 96% |
| Washington, MD | 147,430 | 10% | 100% |
| Charles, MD | 146,551 | 13% | 100% |
| St. Mary's, MD | 105,151 | 16% | 100% |
| Allegany, MD | 75,087 | 9% | 100% |
| Howard, MD | 287,085 | 1% | 24% |
| Anne Arundel, MD | 537,656 | 1% | 7% |
| Garrett, MD | 30,097 | 14% | 100% |
| Calvert, MD | 88,737 | 1% | 8% |
| Germantown, MD | 86,395 | 0% | 100% |
| Silver Spring, MD | 71,452 | 0% | 100% |
| Waldorf, MD | 67,752 | 1% | 100% |
| Frederick, MD | 65,239 | 0% | 100% |
| Rockville, MD | 61,209 | 0% | 100% |
| Bethesda, MD | 60,858 | 0% | 100% |
| Gaithersburg, MD | 59,933 | 0% | 100% |
| Bowie, MD | 54,727 | 0% | 100% |
| Aspen Hill, MD | 48,759 | 0% | 100% |
| Wheaton, MD | 48,284 | 0% | 100% |
| Potomac, MD | 44,965 | 1% | 100% |
| North Bethesda, MD | 43,828 | 0% | 100% |
| Hagerstown, MD | 39,662 | 0% | 100% |
| Clinton, MD | 35,970 | 1% | 100% |
| Olney, MD | 33,844 | 0% | 100% |
| Chillum, MD | 33,513 | 0% | 100% |
| Montgomery Village, MD | 32,032 | 0% | 100% |
| College Park, MD | 30,413 | 0% | 100% |
| South Laurel, MD | 26,112 | 0% | 100% |
| Suitland, MD | 25,825 | 0% | 100% |
| Laurel, MD | 25,115 | 0% | 100% |
| North Potomac, MD | 24,410 | 0% | 100% |
| Scaggsville, MD | 24,333 | 0% | 100% |
| Fort Washington, MD | 23,717 | 0% | 100% |
| Fairland, MD | 23,681 | 0% | 100% |
| Greenbelt, MD | 23,068 | 0% | 100% |
| Cumberland, MD | 20,859 | 0% | 100% |
| Camp Springs, MD | 19,096 | 0% | 100% |
| Beltsville, MD | 16,772 | 0% | 100% |
| Takoma Park, MD | 16,715 | 0% | 100% |
| Hillcrest Heights, MD | 16,469 | 0% | 100% |
| Glassmanor, MD | 17,295 | 0% | 100% |
| Redland, MD | 17,242 | 0% | 100% |
| Beltsville, MD | 16,772 | 0% | 100% |
| Takoma Park, MD | 16,715 | 0% | 100% |
| Hillcrest Heights, MD | 16,469 | 0% | 100% |
| Maryland City, MD | 16,093 | 0% | 100% |
| East Riverdale, MD | 15,509 | 0% | 100% |
| Damascus, MD | 15,257 | 0% | 100% |
| Cloverly, MD | 15,126 | 0% | 100% |
| Adelphi, MD | 15,086 | 0% | 100% |
| Colesville, MD | 14,647 | 0% | 100% |
| Clarksburg, MD | 13,766 | 0% | 100% |
| Glenmont, MD | 13,529 | 0% | 100% |
| Glenn Dale, MD | 13,466 | 0% | 100% |
Largest telephone carriers in area code 240
This table provides a quick overview of nearby area codes, their locations, and some historical context for each.
| Carrier | Landline Market Share | Wireless Market Share |
|---|---|---|
| Verizon | 9% | - |
| Xo | 6% | - |
| Peerless Network | 5% | - |
| Global Crossing Local Services | 4% | - |
| Broadwing | 4% | - |
| Cavalier East | 3% | - |
| Core | 3% | - |
| Other | 27% | - |
| Sprint | - | 14% |
| Verizon Wireless | - | 9% |
| Cingular | - | 7% |
| Omnipoint Cap Operations | - | 4% |
| Cricket Comm | - | 2% |
| United States Cel Md | - | 1% |
| 365 Wireless | - | 1% |
| Other | - | 1% |
Prefixes in Area Code 240
Below is the list of some of Prefixes in area code 240
| Prefix | Usage | Primary City | Carrier | Introduction Date |
|---|---|---|---|---|
| (240) 200- | landline | Mount Rainier | Bandwidth.com | 10/04/2010 |
| (240) 201- | landline | Ridge | Peerless Network Of The District Of Columbia, DC | 07/22/1999 |
| (240) 203- | wireless | Hagerstown | Sprint | 10/04/2011 |
| (240) 204- | wireless | Bethesda | Verizon Wireless | 09/07/2011 |
| (240) 205- | wireless | Cabin John | Cingular Wireless | 07/23/2003 |
| (240) 206- | landline | Glenn Dale | Xo Maryland | 10/31/2001 |
| (240) 207- | landline | Damascus | Cavalier East | 08/20/2000 |
| (240) 208- | landline | La Plata | Peerless Network Of The District Of Columbia, DC | 07/22/1999 |
| (240) 209- | landline | Indian Head | Peerless Network Of The District Of Columbia, DC | 07/22/1999 |
| (240) 210- | wireless | Waldorf | Cingular Wireless | 08/20/2000 |
| (240) 212- | landline | Oakland | Core Comms | 06/13/2000 |
| (240) 213- | landline | Waldorf | Peerless Network Of The District Of Columbia, DC | 07/22/1999 |
| (240) 214- | landline | Mechanicsville | Peerless Network Of The District Of Columbia, DC | 07/22/1999 |
| (240) 215- | landline | Frederick | Telcove Operations | 01/14/2000 |
| (240) 216- | wireless | Waldorf | Sprint | 03/15/2001 |
| (240) 217- | wireless | Hagerstown | Omnipoint Comms Cap Operations | 04/16/2001 |
| (240) 218- | landline | Nanjemoy | Peerless Network Of The District Of Columbia, DC | 02/27/1999 |
| (240) 220- | landline | Poolesville | Peerless Network | 02/27/1999 |
| (240) 221- | landline | Rockville | 05/10/1999 | |
| (240) 222- | landline | Waldorf | Cavalier Telephone Mid-atlantic | 08/20/2000 |
| (240) 223- | landline | Mount Rainier | Allegiance Telecom | 02/27/1999 |
| (240) 224- | wireless | Gaithersburg | Verizon Wireless | 09/10/2012 |
| (240) 225- | landline | Frederick | Core Comms | 06/13/2000 |
| (240) 228- | landline | Laurel | 11/20/1998 | |
| (240) 229- | landline | Waldorf | Broadwing Comms. | 07/22/1999 |
| (240) 230- | landline | Hughesville | Global Crossing Local Services | 05/10/1999 |
| (240) 231- | landline | Hagerstown | Core Comms | 06/13/2000 |
| (240) 232- | landline | Mount Rainier | Broadwing Comms. | 07/22/1999 |
| (240) 233- | landline | Newburg | Teleport Comms America | 02/27/1999 |
| (240) 234- | wireless | Mount Rainier | Verizon Wireless | 10/04/2011 |
| (240) 235- | landline | Bethesda | Paetec Comms | 10/13/1999 |
| (240) 236- | landline | Frederick | 06/13/2000 | |
| (240) 237- | landline | Callaway | Teleport Comms America | 02/27/1999 |
| (240) 238- | landline | Rockville | Paetec Comms | 10/13/1999 |
| (240) 239- | landline | Leonardtown | Core Comms | 10/31/2000 |
| (240) 241- | landline | Chevy Chase | Starpower Comms | 02/27/1999 |
| (240) 242- | landline | Kensington | Starpower Comms | 02/27/1999 |
| (240) 243- | landline | Gaithersburg | Allegiance Telecom | 01/14/2000 |
| (240) 244- | landline | Mount Rainier | Starpower Comms | 02/27/1999 |
| (240) 245- | landline | Glenn Dale | Starpower Comms | 02/27/1999 |
| (240) 246- | landline | Gaithersburg | Starpower Comms | 11/20/1998 |
| (240) 247- | landline | Mount Rainier | Allegiance Telecom | 02/27/1999 |
| (240) 248- | landline | Ridge | Peerless Network | 02/27/1999 |
| (240) 249- | landline | Mechanicsville | Teleport Comms America | 02/27/1999 |
| (240) 250- | landline | Brandywine | Peerless Network | 02/27/1999 |
| (240) 251- | landline | Highfield | Core Comms | 06/13/2000 |
| (240) 252- | landline | Gaithersburg | Level 3 Comms | 05/10/1999 |
| (240) 253- | landline | Mount Rainier | Global Crossing Local Services | 02/27/1999 |
| (240) 254- | landline | Hughesville | Teleport Comms America | 02/27/1999 |
| (240) 255- | landline | Poolesville | Peerless Network | 07/22/1999 |
| (240) 256- | landline | Leonardtown | Teleport Comms America | 02/27/1999 |
| (240) 257- | landline | Nanjemoy | Teleport Comms America | 02/27/1999 |
| (240) 258- | landline | Ridge | Teleport Comms America | 02/27/1999 |
| (240) 260- | landline | Mount Rainier | Allegiance Telecom | 06/13/2000 |
| (240) 262- | wireless | Callaway | Sprint | 10/17/2011 |
| (240) 263- | wireless | Bethesda | Sprint | 11/10/2011 |
| (240) 264- | landline | Beltsville | 02/27/1999 | |
| (240) 265- | wireless | Bethesda | Sprint | 11/10/2011 |
| (240) 266- | landline | Mount Rainier | Peerless Network | 02/27/1999 |
| (240) 268- | landline | Rockville | Allegiance Telecom | 02/27/1999 |
| (240) 269- | landline | Mount Rainier | Peerless Network | 02/27/1999 |
| (240) 270- | wireless | Waldorf | Verizon Wireless | 11/07/2011 |
| (240) 271- | wireless | Bethesda | Cingular Wireless | 02/27/1999 |
| (240) 272- | wireless | Bethesda | Sprint | 11/10/2011 |
| (240) 273- | landline | Mount Rainier | Broadwing Comms. | 07/22/1999 |
| (240) 274- | wireless | Bethesda | Cingular Wireless | 02/27/1999 |
| (240) 275- | landline | Grantsville | Core Comms | 10/31/2000 |
| (240) 276- | landline | Rockville | 05/04/2004 | |
| (240) 277- | wireless | Bethesda | Sprint | 10/18/2002 |
| (240) 278- | wireless | Laurel | Verizon Wireless | 07/08/2011 |
| (240) 279- | landline | Waldorf | Core Comms | 10/31/2000 |
| (240) 280- | landline | Laurel | Comcast Phone Of Northern Maryland | 03/03/2001 |
| (240) 281- | wireless | Bethesda | Cingular Wireless | 10/13/1999 |
| (240) 282- | landline | Mechanicsville | Peerless Network | 02/27/1999 |
| (240) 283- | landline | Kensington | Paetec Comms | 10/13/1999 |
| (240) 284- | landline | Frostburg | Level 3 Comms | 11/01/2004 |
| (240) 285- | landline | Frederick | Verizon Wireless | 06/13/2000 |
| (240) 286- | wireless | Bethesda | Sprint | 09/17/2002 |
| (240) 287- | landline | Hancock | Core Comms | 06/13/2000 |
| (240) 288- | landline | Thurmont | Comcast Phone Of Northern Maryland | 11/01/2004 |
| (240) 289- | landline | Oxon Hill | Cavalier Telephone Mid-atlantic | 08/20/2000 |
| (240) 290- | landline | Mount Rainier | Allegiance Telecom | 02/27/1999 |
| (240) 291- | wireless | Hagerstown | Cingular Wireless | 10/15/2002 |
| (240) 292- | landline | Kensington | 10/13/1999 | |
| (240) 293- | landline | Mount Rainier | Starpower Comms | 02/27/1999 |
| (240) 294- | landline | Laurel | Xo Maryland | 06/30/2001 |
| (240) 295- | landline | Laurel | Cavalier Telephone Mid-atlantic | 08/20/2000 |
| (240) 296- | landline | Hyattsville | Cavalier Telephone Mid-atlantic | 08/20/2000 |
| (240) 297- | landline | College Park | Level 3 Comms | 10/13/1999 |
| (240) 298- | wireless | Leonardtown | Verizon Wireless | 10/13/1999 |
| (240) 299- | wireless | Waldorf | Sprint | 10/13/1999 |
| (240) 300- | wireless | Waldorf | Verizon Wireless | 12/07/2010 |
| (240) 303- | landline | Clinton | Cavalier Telephone Mid-atlantic | 08/20/2000 |
| (240) 304- | wireless | Mount Rainier | Sprint | 07/03/2002 |
| (240) 305- | wireless | Beltsville | Sprint | 02/27/1999 |
| (240) 306- | landline | Gaithersburg | Allegiance Telecom | 06/13/2000 |
| (240) 307- | landline | Emmitsburg | AT&T; Local | 03/27/2003 |
| (240) 308- | wireless | Damascus | Cingular Wireless | 08/20/2000 |
| (240) 309- | wireless | Leonardtown | Verizon Wireless | 09/10/2012 |
| (240) 310- | wireless | Hagerstown | Uscoc Of Cumberland DBA United States Cel Md | 02/27/1999 |
| (240) 312- | landline | Capitol Heights | Cavalier Telephone Mid-atlantic | 08/20/2000 |
| (240) 313- | landline | Hagerstown | 10/31/2000 | |
| (240) 314- | landline | Rockville | 06/13/2000 | |
| (240) 315- | landline | Frederick | 08/20/2000 | |
| (240) 316- | wireless | Chevy Chase | Sprint | |
| (240) 317- | landline | Callaway | Starpower Comms | 11/20/1998 |
| (240) 318- | landline | Clinton | 01/14/2000 | |
| (240) 319- | wireless | Columbia | Verizon Wireless | 06/06/2008 |
| (240) 320- | landline | Waldorf | Cavalier East | 10/31/2000 |
| (240) 321- | wireless | Oakland | Uscoc Of Cumberland DBA United States Cel Md | 02/27/1999 |
| (240) 322- | landline | Mccoole | Core Comms | 10/31/2000 |
| (240) 323- | landline | Emmitsburg | Core Comms | 10/31/2000 |
| (240) 324- | landline | Clarksville | Ymax Comms Corp. | 10/08/2008 |
| (240) 325- | landline | Damascus | Core Comms | 10/31/2000 |
| (240) 326- | landline | Upper Marlboro | Cavalier Telephone Mid-atlantic | 08/20/2000 |
| (240) 327- | landline | Gaithersburg | Core Comms | 10/31/2000 |
| (240) 328- | landline | Rockville | 08/20/2000 | |
| (240) 329- | landline | Hagerstown | Level 3 Comms | 10/31/2000 |
| (240) 330- | wireless | Cabin John | Sprint | 12/14/2007 |
| (240) 331- | landline | Mount Rainier | Peerless Network | 02/27/1999 |
| (240) 332- | landline | Newburg | Peerless Network | 02/27/1999 |
| (240) 333- | landline | Mount Rainier | Cavalier East | 05/09/2001 |
| (240) 334- | landline | Mount Rainier | Global Crossing Local Services | 02/27/1999 |
| (240) 335- | landline | Glenn Dale | Cavalier Telephone Mid-atlantic | 08/20/2000 |
| (240) 336- | landline | Bethesda | Core Comms | 10/31/2000 |
| (240) 337- | landline | Mount Rainier | Peerless Network | 02/27/1999 |
| (240) 338- | wireless | Silver Spring | Verizon Wireless | 01/14/2000 |
| (240) 339- | landline | Upper Marlboro | Cavalier East | 10/31/2000 |
| (240) 340- | wireless | Bethesda | Sprint | 08/18/2011 |
| (240) 341- | landline | Adamstown | Mci Worldcom Comms | 02/25/2009 |
| (240) 342- | landline | Sandy Spring | Starpower Comms | 11/20/1998 |
| (240) 343- | wireless | Hancock | Verizon Wireless | 05/10/2011 |
| (240) 344- | wireless | Frederick | Cingular Wireless | 10/15/2002 |
| (240) 345- | landline | Sandy Spring | Level 3 Comms | 03/09/2006 |
| (240) 346- | wireless | Waldorf | Sprint | 08/20/2000 |
| (240) 347- | landline | Hagerstown | Bandwidth.com | 08/04/2008 |
| (240) 348- | landline | Oxon Hill | Level 3 Comms | 08/20/2000 |
| (240) 349- | landline | La Plata | Global Crossing Local Services | 05/10/1999 |
| (240) 350- | wireless | Beltsville | Sprint | 05/10/1999 |
| (240) 351- | wireless | Beltsville | Sprint | 05/10/1999 |
| (240) 352- | landline | La Plata | Peerless Network | 02/27/1999 |
| (240) 353- | wireless | Beltsville | Sprint | 05/10/1999 |
| (240) 354- | wireless | Beltsville | Sprint | 05/10/1999 |
| (240) 355- | wireless | Beltsville | Sprint | 05/10/1999 |
| (240) 356- | landline | Frederick | Level 3 Comms | 03/03/2001 |
| (240) 357- | wireless | Frederick | Verizon Wireless | 06/12/2006 |
| (240) 358- | landline | Damascus | Peerless Network | 02/27/1999 |
| (240) 359- | landline | Indian Head | Peerless Network | 02/27/1999 |
| (240) 360- | wireless | Laurel | Omnipoint Comms Cap Operations | 09/17/2013 |
| (240) 361- | landline | Gaithersburg | Cavalier Telephone Mid-atlantic | 08/20/2000 |
| (240) 362- | landline | Cumberland | 02/27/1999 | |
| (240) 363- | landline | Kensington | Global Naps South | 02/27/1999 |
| (240) 364- | landline | Gaithersburg | Cavalier East | 05/09/2001 |
| (240) 365- | landline | Damascus | Baltimore-washington Telephone (bwt) | 08/20/2000 |
| (240) 366- | landline | Williamsport | AT&T; Local | 03/03/2001 |
| (240) 367- | wireless | Frederick | Sprint | 10/18/2002 |
| (240) 368- | landline | Waldorf | Peerless Network | 02/27/1999 |
| (240) 369- | landline | Mount Airy | Core Comms | 10/31/2000 |
| (240) 370- | wireless | Bethesda | Sprint | 12/14/2007 |
| (240) 371- | landline | Mount Rainier | Peerless Network | 02/27/1999 |
| (240) 372- | wireless | Gaithersburg | Sprint | 10/13/1999 |
| (240) 373- | landline | Odenton | 11/20/1998 | |
| (240) 374- | landline | Laurel | Global Crossing Local Services | 02/27/1999 |
| (240) 375- | wireless | Capitol Heights | Sprint | 11/20/1998 |
| (240) 376- | landline | Hughesville | Peerless Network | 02/27/1999 |
| (240) 377- | landline | Indian Head | Global Crossing Local Services | 05/10/1999 |
| (240) 378- | landline | Cumberland | Core Comms | 10/31/2000 |
| (240) 379- | landline | Frederick | 03/03/2001 | |
| (240) 380- | wireless | Cabin John | Verizon Wireless | 09/17/2007 |
| (240) 381- | wireless | Silver Spring | Cingular Wireless | 01/14/2000 |
| (240) 382- | landline | Hagerstown | Teleport Comms America | 06/11/2009 |
| (240) 383- | wireless | Chevy Chase | Cingular Wireless | 08/20/2000 |
| (240) 384- | landline | Callaway | Peerless Network | 02/27/1999 |
| (240) 385- | landline | Myersville | 10/31/2000 | |
| (240) 386- | landline | Gaithersburg | 08/20/2000 | |
| (240) 387- | landline | Chevy Chase | Cavalier East | 01/14/2000 |
| (240) 388- | wireless | Gaithersburg | Sprint | 11/04/2002 |
| (240) 389- | landline | Sandy Spring | Atx Telecom Services, Ltd | 06/30/2001 |
| (240) 390- | landline | Sandy Spring | Cavalier Telephone Mid-atlantic | 08/20/2000 |
| (240) 391- | landline | Mount Rainier | Global Crossing Local Services | 02/27/1999 |
| (240) 392- | landline | Oxon Hill | Starpower Comms | 02/27/1999 |
| (240) 393- | wireless | Cabin John | Verizon Wireless | 06/13/2000 |
| (240) 394- | wireless | Mount Airy | Cingular Wireless | 12/13/2004 |
| (240) 395- | landline | Bethesda | Cavalier Telephone Mid-atlantic | 08/20/2000 |
| (240) 396- | landline | Mount Rainier | Global Crossing Local Services | 02/27/1999 |
| (240) 397- | wireless | Frederick | Verizon Wireless | 03/06/2009 |
| (240) 398- | wireless | Cabin John | Sprint | 07/03/2002 |
| (240) 399- | landline | Chevy Chase | Xo Maryland | 10/13/1999 |
| (240) 400- | wireless | Bethesda | Sprint | 08/18/2011 |
| (240) 401- | wireless | Rockville | Cingular Wireless | 11/20/1998 |
| (240) 402- | landline | College Park | Mci Worldcom Comms | 09/21/2010 |
| (240) 403- | landline | Rockville | Cavalier Telephone Mid-atlantic | 08/20/2000 |
| (240) 404- | landline | Gaithersburg | Xo Maryland | 02/13/2001 |
| (240) 405- | landline | Frederick | Us Lec | 07/27/2004 |
| (240) 406- | wireless | Rockville | Leap Wireless Intl DBA Cricket Comm | 09/17/2009 |
| (240) 407- | landline | Mount Rainier | Global Crossing Local Services | 02/27/1999 |
| (240) 408- | wireless | Rockville | Leap Wireless Intl DBA Cricket Comm | 10/14/2009 |
| (240) 409- | wireless | Frederick | Cingular Wireless | 02/27/1999 |
| (240) 412- | wireless | Waldorf | Sprint | 01/16/2001 |
| (240) 413- | wireless | Hyattsville | Omnipoint Comms Cap Operations | 03/12/2001 |
| (240) 414- | landline | Mount Rainier | Peerless Network | 02/27/1999 |
| (240) 415- | landline | Frederick | Ymax Comms Corp. | 12/16/2008 |
| (240) 416- | wireless | Waldorf | Cingular Wireless | 05/18/2001 |
| (240) 417- | wireless | Capitol Heights | Sprint | 03/03/2001 |
| (240) 418- | wireless | Beltsville | Sprint | 11/12/2001 |
| (240) 419- | wireless | Waldorf | Verizon Wireless | 10/29/2007 |
| (240) 420- | landline | Hagerstown | 07/22/1999 | |
| (240) 421- | wireless | Rockville | Omnipoint Comms Cap Operations | 04/09/2001 |
| (240) 422- | wireless | Frederick | Omnipoint Comms Cap Operations | 05/15/2002 |
| (240) 423- | wireless | Silver Spring | Omnipoint Comms Cap Operations | 05/21/2001 |
| (240) 424- | wireless | Mount Rainier | Sprint | 11/16/2007 |
| (240) 425- | landline | Cabin John | Dslnet Comms Va | 01/25/2001 |
| (240) 426- | wireless | Bethesda | Sprint | 10/25/2001 |
| (240) 427- | landline | Waldorf | Xo Maryland | 04/23/2001 |
| (240) 428- | landline | Rockville | Bandwidth.com | 10/14/2009 |
| (240) 429- | wireless | Silver Spring | Verizon Wireless | 12/19/2006 |
| (240) 430- | landline | Kensington | Cavalier Telephone Mid-atlantic | 08/20/2000 |
| (240) 431- | wireless | Tall Timbers | Sprint | 10/31/2000 |
| (240) 432- | wireless | Beltsville | Sprint | 02/27/1999 |
| (240) 433- | landline | Silver Spring | Cavalier Telephone Mid-atlantic | 08/20/2000 |
| (240) 434- | landline | Leonardtown | Broadwing Comms. | 10/31/2000 |
| (240) 435- | wireless | Waldorf | Verizon Wireless | 05/07/2009 |
| (240) 436- | landline | Ijamsville | Telcove Operations | 08/20/2000 |
| (240) 437- | landline | Sandy Spring | Xo Maryland | 06/30/2001 |
| (240) 438- | wireless | Silver Spring | Sprint | 08/15/2011 |
| (240) 439- | wireless | Frederick | Verizon Wireless | 06/06/2008 |
| (240) 440- | wireless | Frederick | Leap Wireless Intl DBA Cricket Comm | 02/27/2009 |
| (240) 441- | wireless | Oxon Hill | Omnipoint Comms Cap Operations | 06/06/2001 |
| (240) 442- | landline | Oakland | 05/22/2001 | |
| (240) 444- | wireless | Laurel | Verizon Wireless | 09/07/2011 |
| (240) 445- | wireless | Bethesda | Sprint | 11/10/2011 |
| (240) 446- | wireless | Frederick | Verizon Wireless | 08/09/2001 |
| (240) 447- | wireless | Rockville | Cingular Wireless | 02/27/1999 |
| (240) 448- | wireless | Waldorf | Sprint | 09/07/2011 |
| (240) 449- | wireless | Gaithersburg | Cingular Wireless | 03/03/2001 |
| (240) 450- | landline | Silver Spring | Cavalier Telephone Mid-atlantic | 08/20/2000 |
| (240) 452- | landline | Hagerstown | Lumos Networks | 07/22/2010 |
| (240) 453- | landline | Rockville | 11/20/1998 | |
| (240) 454- | wireless | Gaithersburg | Paetec Comms | 04/22/2005 |
| (240) 455- | landline | Oxon Hill | Paetec Comms | 06/20/2001 |
| (240) 456- | landline | Laurel | 08/20/2000 | |
| (240) 457- | wireless | Frederick | Verizon Wireless | 09/04/2008 |
| (240) 458- | wireless | Waldorf | Verizon Wireless | 10/04/2011 |
| (240) 459- | wireless | Laurel | Verizon Wireless | 07/27/2010 |
| (240) 460- | wireless | Silver Spring | Cingular Wireless | 07/22/1999 |
| (240) 461- | wireless | Silver Spring | Cingular Wireless | 07/22/1999 |
| (240) 462- | wireless | Beltsville | Sprint | 02/27/1999 |
| (240) 463- | wireless | Silver Spring | Cingular Wireless | 02/27/1999 |
| (240) 464- | landline | Chevy Chase | Sprint | 05/10/1999 |
| (240) 465- | landline | Mount Rainier | Peerless Network | 02/27/1999 |
| (240) 466- | wireless | Mechanicsville | Cingular Wireless | 10/31/2001 |
| (240) 467- | landline | Oxon Hill | Comcast Phone Of Northern Maryland | 04/25/2013 |
| (240) 468- | wireless | Mount Rainier | Sprint | 11/16/2007 |
| (240) 469- | wireless | Hagerstown | Sprint | 02/14/2008 |
| (240) 470- | wireless | Laurel | Verizon Wireless | 10/04/2011 |
| (240) 471- | landline | Silver Spring | Global Crossing Local Services | 02/27/1999 |
| (240) 472- | wireless | Silver Spring | Cingular Wireless | 08/20/2000 |
| (240) 473- | landline | College Park | Cavalier Telephone Mid-atlantic | 08/20/2000 |
| (240) 475- | wireless | Silver Spring | Cingular Wireless | 08/20/2000 |
| (240) 476- | wireless | Silver Spring | Omnipoint Comms Cap Operations | 02/21/2001 |
| (240) 477- | landline | Gaithersburg | Lightwave Comms | 05/20/2005 |
| (240) 478- | wireless | Cabin John | Cingular Wireless | 07/27/2004 |
| (240) 479- | wireless | Oxon Hill | Verizon Wireless | 04/07/2008 |
| (240) 480- | wireless | Bethesda | Sprint | 09/27/2010 |
| (240) 481- | wireless | Silver Spring | Omnipoint Comms Cap Operations | 05/11/2001 |
| (240) 482- | landline | Cabin John | Us Lec | 01/14/2000 |
| (240) 483- | landline | Oxon Hill | Comcast Phone Of Northern Maryland | 10/31/2001 |
| (240) 485- | landline | Cabin John | Us Lec | 01/14/2000 |
| (240) 486- | wireless | Glenn Dale | Omnipoint Comms Cap Operations | 03/12/2001 |
| (240) 487- | landline | Hyattsville | Us Lec | 01/14/2000 |
| (240) 488- | landline | Oakland | Shentel Comms | 05/16/2012 |
| (240) 489- | landline | Poolesville | Xo Maryland | 02/13/2001 |
| (240) 490- | wireless | Middletown | Omnipoint Comms Cap Operations | 06/12/2001 |
| (240) 491- | landline | Mount Rainier | Global Crossing Local Services | 02/27/1999 |
| (240) 492- | landline | Capitol Heights | Us Lec | 01/14/2000 |
| (240) 493- | landline | Oxon Hill | Us Lec | 01/14/2000 |
| (240) 494- | landline | Mount Rainier | Cavalier East | 05/09/2001 |
| (240) 495- | wireless | Mount Rainier | Verizon Wireless | 10/29/2013 |
| (240) 497- | landline | Chevy Chase | 10/31/2000 | |
| (240) 498- | wireless | Beltsville | Sprint | 10/31/2000 |
| (240) 499- | landline | Cabin John | Us Lec | 01/14/2000 |
| (240) 500- | landline | Hagerstown | Us Lec | 10/21/2010 |
| (240) 501- | wireless | Silver Spring | Sprint | 10/08/2001 |
| (240) 502- | wireless | Silver Spring | Sprint | 10/04/2011 |
| (240) 503- | landline | Newburg | Peerless Network | 04/09/2013 |
| (240) 504- | wireless | Silver Spring | Sprint | 10/04/2011 |
| (240) 505- | wireless | Silver Spring | Omnipoint Comms Cap Operations | 10/31/2001 |
| (240) 506- | wireless | Rockville | Cingular Wireless | 01/09/2002 |
| (240) 507- | wireless | Cabin John | Verizon Wireless | 09/05/2008 |
| (240) 508- | wireless | Capitol Heights | Sprint | 02/27/1999 |
| (240) 509- | landline | Crofton | Bandwidth.com | 03/31/2008 |
| (240) 510- | landline | Upper Marlboro | Xo Maryland | 10/31/2001 |
| (240) 512- | landline | College Park | Core Comms | 08/08/2006 |
| (240) 513- | wireless | Hagerstown | Sprint | 10/19/2011 |
| (240) 514- | landline | Cabin John | Us Lec | 01/14/2000 |
| (240) 515- | wireless | Bethesda | Cingular Wireless | 06/20/2001 |
| (240) 516- | landline | Silver Spring | Us Lec | 01/14/2000 |
| (240) 518- | wireless | Waldorf | Sprint | 10/21/2011 |
| (240) 519- | wireless | Bethesda | Sprint | 11/10/2011 |
| (240) 520- | wireless | Hagerstown | Sprint | 03/29/2006 |
| (240) 522- | wireless | Cumberland | Sprint | 12/12/2001 |
| (240) 523- | landline | La Plata | Xo Maryland | 02/13/2001 |
| (240) 524- | landline | Laurel | Peerless Network | 02/27/1999 |
| (240) 525- | landline | Upper Marlboro | Peerless Network | 02/27/1999 |
| (240) 526- | landline | Leonardtown | Peerless Network | 02/27/1999 |
| (240) 527- | landline | Hagerstown | 10/31/2000 | |
| (240) 528- | landline | Hughesville | Broadwing Comms. | 10/31/2000 |
| (240) 529- | landline | Frederick | 10/31/2000 | |
| (240) 530- | landline | Waldorf | Local Access | 08/01/2013 |
| (240) 532- | wireless | Oxon Hill | Verizon Wireless | 10/29/2013 |
| (240) 533- | landline | Mount Rainier | Teleport Comms America | 07/22/1999 |
| (240) 535- | wireless | Silver Spring | Cingular Wireless | 01/09/2001 |
| (240) 536- | landline | Sandy Spring | Peerless Network | 02/27/1999 |
| (240) 538- | landline | Leonardtown | Xo Maryland | 02/13/2001 |
| (240) 539- | landline | Mount Rainier | Peerless Network | 02/27/1999 |
| (240) 541- | wireless | Bethesda | Sprint | 10/31/2011 |
| (240) 542- | landline | College Park | Us Lec | 01/14/2000 |
| (240) 543- | wireless | Bethesda | Sprint | 07/25/2006 |
| (240) 544- | landline | Glenn Dale | Us Lec | 01/14/2000 |
| (240) 545- | landline | Upper Marlboro | Us Lec | 01/14/2000 |
| (240) 546- | landline | Clinton | Us Lec | 01/14/2000 |
| (240) 547- | landline | Laurel | Level 3 Comms | 07/22/1999 |
| (240) 548- | landline | Mount Rainier | Allegiance Telecom | 10/31/2000 |
| (240) 550- | wireless | Rockville | Leap Wireless Intl DBA Cricket Comm | 03/26/2009 |
| (240) 551- | wireless | Rockville | Leap Wireless Intl DBA Cricket Comm | 03/25/2009 |
| (240) 552- | wireless | Rockville | Leap Wireless Intl DBA Cricket Comm | 03/25/2009 |
| (240) 553- | landline | Mount Rainier | Allegiance Telecom | 08/20/2000 |
| (240) 554- | landline | Laurel | Allegiance Telecom | 10/31/2000 |
| (240) 556- | landline | Glenn Dale | Paetec Comms | 10/31/2001 |
| (240) 558- | landline | Kensington | Cavalier Telephone Mid-atlantic | 06/30/2001 |
| (240) 559- | landline | Sandy Spring | Allegiance Telecom | 10/31/2000 |
| (240) 560- | landline | Chevy Chase | Xo Maryland | 04/23/2001 |
| (240) 561- | wireless | Leonardtown | Verizon Wireless | 07/07/2008 |
| (240) 565- | wireless | Laurel | Omnipoint Comms Cap Operations | 12/30/2005 |
| (240) 566- | landline | Frederick | 06/11/2002 | |
| (240) 567- | landline | Rockville | 07/12/2006 | |
| (240) 568- | landline | Laurel | 07/22/1999 | |
| (240) 573- | landline | Upper Marlboro | Global Crossing Local Services | 07/22/1999 |
| (240) 575- | landline | Frederick | Level 3 Comms | 12/30/2005 |
| (240) 577- | wireless | Leonardtown | Verizon Wireless | 08/09/2006 |
| (240) 578- | wireless | Frederick | Verizon Wireless | 07/08/2011 |
| (240) 580- | wireless | Cumberland | Sprint | 06/14/2001 |
| (240) 581- | landline | Laurel | Paetec Comms | 03/03/2001 |
| (240) 582- | landline | Hyattsville | 07/22/1999 | |
| (240) 583- | landline | Beltsville | 04/28/2010 | |
| (240) 585- | wireless | Waldorf | Verizon Wireless | 06/29/2011 |
| (240) 586- | landline | Frederick | 12/22/2006 | |
| (240) 587- | wireless | Leonardtown | Verizon Wireless | 07/06/2009 |
| (240) 593- | wireless | Laurel | Omnipoint Comms Cap Operations | 03/13/2001 |
| (240) 595- | wireless | Chevy Chase | Verizon Wireless | 09/13/2006 |
| (240) 597- | landline | Gaithersburg | Peerless Network | 02/27/1999 |
| (240) 599- | landline | Rockville | Broadwing Comms. | 07/22/1999 |
| (240) 600- | wireless | Mount Rainier | Sprint | 04/27/2011 |
| (240) 601- | wireless | Beltsville | Sprint | 07/22/1999 |
| (240) 602- | wireless | Beltsville | Sprint | 07/22/1999 |
| (240) 603- | wireless | Beltsville | Sprint | 07/22/1999 |
| (240) 604- | wireless | Beltsville | Sprint | 07/22/1999 |
| (240) 605- | wireless | Beltsville | Sprint | 07/22/1999 |
| (240) 606- | wireless | Beltsville | Sprint | 07/22/1999 |
| (240) 607- | landline | Waldorf | Global Crossing Local Services | 05/10/1999 |
| (240) 608- | wireless | Frederick | 365 Wireless | 03/11/2013 |
| (240) 612- | landline | Mount Rainier | Tw Telecom | 08/04/2010 |
| (240) 613- | landline | Hyattsville | Us Lec | 04/05/2012 |
| (240) 614- | wireless | Rockville | Metro PCS | 07/16/2013 |
| (240) 615- | wireless | Hyattsville | Metro PCS | 05/29/2013 |
| (240) 616- | landline | College Park | Mci Worldcom Comms | 06/30/2001 |
| (240) 617- | Shentel Comms | 05/12/2014 | ||
| (240) 619- | landline | Chevy Chase | Mci Worldcom Comms | 08/20/2000 |
| (240) 620- | landline | Rockville | Mci Worldcom Comms | 08/20/2000 |
| (240) 621- | landline | Kensington | Mci Worldcom Comms | 08/20/2000 |
| (240) 624- | landline | Greenbelt | 06/13/2000 | |
| (240) 625- | wireless | Hagerstown | Sprint | 04/17/2001 |
| (240) 626- | wireless | Frederick | Sprint | 05/10/1999 |
| (240) 627- | landline | Mount Rainier | Global Crossing Local Services | 02/27/1999 |
| (240) 629- | landline | Frederick | 10/13/1999 | |
| (240) 630- | landline | Mount Rainier | Bandwidth.com | 10/31/2011 |
| (240) 631- | landline | Gaithersburg | 11/20/1998 | |
| (240) 632- | landline | Gaithersburg | 07/22/1999 | |
| (240) 638- | landline | Mount Rainier | Broadwing Comms. | 05/10/1999 |
| (240) 640- | wireless | Waldorf | Leap Wireless Intl DBA Cricket Comm | 03/24/2009 |
| (240) 643- | wireless | Silver Spring | Omnipoint Comms Cap Operations | 05/16/2002 |
| (240) 644- | landline | Chevy Chase | Xo Maryland | 10/31/2000 |
| (240) 645- | landline | Chevy Chase | Xo Maryland | 10/31/2000 |
| (240) 646- | landline | Laurel | Cavalier East | 10/13/1999 |
| (240) 650- | landline | Cabin John | Broadvox-clec | 11/17/2011 |
| (240) 651- | wireless | Frederick | Halo Wireless Services | 11/28/2011 |
| (240) 652- | landline | Mechanicsville | Xo Maryland | 02/13/2001 |
| (240) 654- | wireless | Gaithersburg | Cingular Wireless | 05/19/2006 |
| (240) 662- | landline | Silver Spring | 01/14/2000 | |
| (240) 667- | landline | Mount Rainier | Global Crossing Local Services | 02/27/1999 |
| (240) 668- | landline | Damascus | Starpower Comms | 11/20/1998 |
| (240) 669- | landline | Kensington | Comcast Phone Of Northern Maryland | 10/31/2000 |
| (240) 670- | landline | Mount Rainier | Local Access | 03/06/2012 |
| (240) 671- | wireless | Mount Rainier | Sprint | 10/31/2000 |
| (240) 672- | landline | Rockville | Verizon Wireless | 10/31/2000 |
| (240) 674- | wireless | Frederick | Sprint | 10/13/1999 |
| (240) 675- | wireless | Myersville | Cingular Wireless | 05/10/1999 |
| (240) 676- | wireless | Silver Spring | Verizon Wireless | 02/27/1999 |
| (240) 678- | wireless | Silver Spring | Verizon Wireless | 02/27/1999 |
| (240) 682- | landline | Waldorf | Starpower Comms | 11/20/1998 |
| (240) 683- | landline | Gaithersburg | 03/03/2001 | |
| (240) 684- | landline | Greenbelt | 10/31/2000 | |
| (240) 685- | landline | Brandywine | Global Crossing Local Services | 05/10/1999 |
| (240) 686- | landline | Gaithersburg | 03/03/2001 | |
| (240) 687- | wireless | Silver Spring | Verizon Wireless | 02/27/1999 |
| (240) 688- | wireless | Silver Spring | Verizon Wireless | 06/12/2006 |
| (240) 691- | landline | Mount Rainier | Global Crossing Local Services | 02/27/1999 |
| (240) 694- | landline | Rockville | 11/20/1998 | |
| (240) 695- | landline | Temple Hills | 11/20/1998 | |
| (240) 696- | landline | Hyattsville | Level 3 Comms | 07/22/1999 |
| (240) 699- | landline | Adamstown | 05/22/2001 | |
| (240) 701- | wireless | Silver Spring | Leap Wireless Intl DBA Cricket Comm | 03/25/2009 |
| (240) 704- | wireless | Mount Rainier | Leap Wireless Intl DBA Cricket Comm | 03/25/2009 |
| (240) 705- | wireless | Chevy Chase | Leap Wireless Intl DBA Cricket Comm | 03/25/2009 |
| (240) 706- | wireless | Chevy Chase | Leap Wireless Intl DBA Cricket Comm | 03/26/2009 |
| (240) 707- | wireless | Hagerstown | Cingular Wireless | 01/27/2012 |
| (240) 708- | wireless | Columbia | Level 3 Comms | 06/08/2012 |
| (240) 712- | wireless | Columbia | Verizon Wireless | 11/01/2011 |
| (240) 713- | landline | Laurel | Peerless Network | 11/02/2011 |
| (240) 715- | landline | Rockville | Global Crossing Local Services | 02/27/1999 |
| (240) 716- | wireless | Mount Rainier | Omnipoint Comms Cap Operations | 11/15/2013 |
| (240) 718- | landline | Callaway | Xo Maryland | 02/13/2001 |
| (240) 720- | landline | Gaithersburg | Global Crossing Local Services | 02/27/1999 |
| (240) 722- | landline | Sandy Spring | Global Crossing Local Services | 02/27/1999 |
| (240) 723- | landline | Silver Spring | Verizon Wireless | 05/10/1999 |
| (240) 724- | landline | Mount Rainier | Cavalier East | 10/31/2000 |
| (240) 725- | landline | Lexington Park | 11/20/1998 | |
| (240) 727- | wireless | Cumberland | Cingular Wireless | 07/22/1999 |
| (240) 731- | wireless | Rockville | Cingular Wireless | 10/31/2000 |
| (240) 734- | landline | Hagerstown | Bandwidth.com | 03/22/2012 |
| (240) 737- | landline | Mount Rainier | Cavalier East | 05/09/2001 |
| (240) 743- | landline | Oxon Hill | Local Access | 11/16/2006 |
| (240) 744- | landline | Mount Rainier | Broadwing Comms. | 05/10/1999 |
| (240) 745- | landline | Damascus | Xo Maryland | 10/31/2001 |
| (240) 747- | landline | Mount Rainier | Cavalier East | 05/09/2001 |
| (240) 750- | wireless | Gaithersburg | Cingular Wireless | 05/06/2005 |
| (240) 751- | landline | Gaithersburg | Telcove Operations | 08/20/2000 |
| (240) 752- | landline | Bethesda | Telcove Operations | 08/20/2000 |
| (240) 753- | landline | Rockville | Telcove Operations | 08/20/2000 |
| (240) 754- | landline | Waldorf | Level 3 Comms | 11/11/2011 |
| (240) 755- | landline | Laurel | Comcast Phone Of Northern Maryland | 01/05/2006 |
| (240) 757- | landline | Mount Rainier | Peerless Network | 07/22/1999 |
| (240) 762- | wireless | Mount Rainier | Verizon Wireless | 08/22/2012 |
| (240) 764- | landline | Chevy Chase | Xo Maryland | 10/31/2000 |
| (240) 765- | landline | Chevy Chase | Xo Maryland | 10/31/2000 |
| (240) 766- | landline | Chevy Chase | Xo Maryland | 10/31/2000 |
| (240) 767- | landline | Capitol Heights | Cavalier East | 05/09/2001 |
| (240) 770- | landline | Oxon Hill | Comcast Phone Of Northern Maryland | 11/22/2004 |
| (240) 772- | wireless | Frederick | Verizon Wireless | 11/17/2011 |
| (240) 773- | landline | Rockville | 10/13/1999 | |
| (240) 776- | landline | La Plata | Broadwing Comms. | 05/10/1999 |
| (240) 777- | landline | Rockville | 05/10/1999 | |
| (240) 778- | landline | Chevy Chase | Xo Maryland | 10/31/2000 |
| (240) 779- | landline | Sandy Spring | Cavalier East | 10/31/2000 |
| (240) 780- | landline | Gaithersburg | Broadwing Comms. | 05/10/1999 |
| (240) 782- | landline | Damascus | Global Crossing Local Services | 05/10/1999 |
| (240) 783- | wireless | Bethesda | Mte DBA Mte Paging Network | 05/10/1999 |
| (240) 784- | wireless | Myersville | Omnipoint Comms Cap Operations | 06/06/2001 |
| (240) 786- | landline | Laurel | Broadwing Comms. | 05/10/1999 |
| (240) 787- | landline | Brandywine | Broadwing Comms. | 05/10/1999 |
| (240) 788- | landline | Oxon Hill | Broadwing Comms. | 05/10/1999 |
| (240) 790- | landline | Mount Rainier | Broadwing Comms. | 05/10/1999 |
| (240) 793- | wireless | Gaithersburg | Sprint | 03/15/2001 |
| (240) 794- | landline | Callaway | Broadwing Comms. | 05/10/1999 |
| (240) 800- | landline | Chevy Chase | Core Comms | 06/22/2012 |
| (240) 801- | wireless | Gaithersburg | Verizon Wireless | 10/04/2013 |
| (240) 802- | wireless | Bethesda | 365 Wireless | 05/10/2013 |
| (240) 803- | wireless | Cumberland | Cingular Wireless | 01/27/2012 |
| (240) 804- | landline | Newburg | Xo Maryland | 04/23/2001 |
| (240) 812- | landline | Poolesville | Global Crossing Local Services | 05/10/1999 |
| (240) 813- | landline | Gaithersburg | Atx Telecom Services, Ltd | 06/30/2001 |
| (240) 818- | landline | Smithsburg | 10/13/1999 | |
| (240) 821- | landline | Silver Spring | Lightwave Comms | 05/27/2005 |
| (240) 823- | landline | Brandywine | Xo Maryland | 02/13/2001 |
| (240) 826- | landline | Rockville | 05/07/2007 | |
| (240) 832- | wireless | Bethesda | Sprint | 05/10/1999 |
| (240) 833- | landline | Chevy Chase | Xo Maryland | 10/31/2000 |
| (240) 837- | landline | Hughesville | Xo Maryland | 02/13/2001 |
| (240) 838- | wireless | Oxon Hill | Omnipoint Comms Cap Operations | 03/12/2001 |
| (240) 839- | wireless | Silver Spring | Verizon Wireless | 01/13/2007 |
| (240) 841- | landline | Laurel | Allegiance Telecom | 10/31/2000 |
| (240) 842- | landline | Glenn Dale | Allegiance Telecom | 10/31/2000 |
| (240) 843- | landline | College Park | Allegiance Telecom | 10/31/2000 |
| (240) 844- | landline | Ridge | Xo Maryland | 02/13/2001 |
| (240) 845- | landline | Chevy Chase | Xo Maryland | 10/31/2000 |
| (240) 846- | landline | Clinton | Xo Maryland | 10/31/2000 |
| (240) 848- | wireless | Gaithersburg | Sprint | 03/03/2001 |
| (240) 855- | wireless | Cabin John | Sprint | 10/09/2006 |
| (240) 857- | landline | Mount Rainier | Tw Telecom | 05/10/1999 |
| (240) 863- | landline | Laurel | Tw Telecom | 05/10/1999 |
| (240) 864- | landline | Rockville | Cavalier East | 05/09/2001 |
| (240) 865- | landline | Baltimore | Level 3 Comms | 03/03/2001 |
| (240) 868- | landline | Mount Rainier | Cavalier East | 05/09/2001 |
| (240) 876- | wireless | Bethesda | Sprint | 11/20/1998 |
| (240) 880- | landline | Chevy Chase | Broadwing Comms. | 07/22/1999 |
| (240) 882- | wireless | Capitol Heights | Sprint | 11/20/1998 |
| (240) 883- | landline | Sandy Spring | Broadwing Comms. | 07/22/1999 |
| (240) 888- | wireless | Rockville | Cingular Wireless | 03/03/2001 |
| (240) 892- | landline | Upper Marlboro | Broadwing Comms. | 07/22/1999 |
| (240) 893- | wireless | Silver Spring | Cingular Wireless | 03/03/2001 |
| (240) 895- | landline | Lexington Park | 06/30/2001 | |
| (240) 897- | landline | Mount Rainier | Broadwing Comms. | 07/22/1999 |
| (240) 898- | landline | Mount Rainier | Broadwing Comms. | 07/22/1999 |
| (240) 899- | wireless | Bethesda | Omnipoint Comms Cap Operations | 03/13/2001 |
| (240) 901- | Centurylink Comms | 05/22/2014 | ||
| (240) 903- | landline | Indian Head | Comcast Phone Of Northern Maryland | 12/03/2013 |
| (240) 912- | landline | Gaithersburg | Us Lec | 01/14/2000 |
| (240) 920- | landline | Cumberland | Level 3 Comms | 05/03/2001 |
| (240) 925- | wireless | Leonardtown | Verizon Wireless | 08/09/2001 |
| (240) 929- | landline | Mount Rainier | Cavalier East | 10/13/1999 |
| (240) 938- | wireless | Ashton | Omnipoint Comms Cap Operations | 06/06/2001 |
| (240) 949- | landline | Mount Rainier | Cavalier East | 05/09/2001 |
| (240) 964- | landline | Cumberland | 05/27/2008 | |
| (240) 965- | landline | College Park | Paetec Comms | 10/31/2000 |
| (240) 976- | Baltimore-washington Telephone (bwt) | 10/17/2005 | ||
| (240) 979- | landline | Cumberland | Level 3 Comms | 03/03/2001 |
| (240) 986- | landline | Nanjemoy | Xo Maryland | 02/13/2001 |
| (240) 988- | wireless | Beltsville | Sprint | 05/10/1999 |
| (240) 993- | landline | Indian Head | Xo Maryland | 02/13/2001 |
| (240) 994- | wireless | Rockville | Verizon Wireless | 10/13/1999 |
| (240) 997- | wireless | Silver Spring | Verizon Wireless | 10/13/1999 |