| District of Maryland area codes: 240 | |
|---|---|
| Country | United States |
| State/Province | Maryland |
| Major City | Baltimore |
| Time Zone | Eastern |
| Prefix | County | Primary City | Company |
|---|---|---|---|
| 240-289 | Prince Georges | Oxon Hill, MD | Cavalier Telephone Mid-atlantic |
| 240-290 | Prince Georges | Mount Rainier, MD | Allegiance Telecom |
| 240-291 | Washington | Hagerstown, MD | New Cingular Wireless PCS - DC |
| 240-292 | Montgomery | Kensington, MD | Verizon Maryland |
| 240-293 | Prince Georges | Mount Rainier, MD | Starpower Communications |
| 240-294 | Prince Georges | Laurel, MD | Xo Maryland |
| 240-295 | Prince Georges | Laurel, MD | Cavalier Telephone Mid-atlantic |
| 240-296 | Prince Georges | Hyattsville, MD | Cavalier Telephone Mid-atlantic |
| 240-297 | Prince Georges | College Park, MD | Level 3 Communications |
| 240-298 | Saint Marys | Leonardtown, MD | Cellco Partnership DBA Verizon Wireless |
| 240-299 | Charles | Waldorf, MD | Sprint Spectrum L.p. |
| 240-300 | Charles | Waldorf, MD | Cellco Partnership DBA Verizon Wireless |
| 240-303 | Prince Georges | Clinton, MD | Cavalier Telephone Mid-atlantic |
| 240-304 | Prince Georges | Mount Rainier, MD | Sprint Spectrum L.p. |
| 240-305 | Prince Georges | Beltsville, MD | Sprint Spectrum L.p. |
| 240-306 | Montgomery | Gaithersburg, MD | Allegiance Telecom |
| 240-307 | Frederick | Emmitsburg, MD | AT&T Local |
| 240-308 | Montgomery | Damascus, MD | New Cingular Wireless PCS - DC |
| 240-309 | Saint Marys | Leonardtown, MD | Cellco Partnership DBA Verizon Wireless |
| 240-310 | Washington | Hagerstown, MD | Uscoc Of Cumberland DBA United States Cel Md |
There are 522 prefixes, In the code area, the major cities are Aspen Hill, MD;Bethesda, MD;Bowie, MD;Chillum, MD;. The major city is Baltimore.