| District of Maryland area codes: 240 | |
|---|---|
| Country | United States |
| State/Province | Maryland |
| Major City | Baltimore |
| Time Zone | Eastern |
| Prefix | County | Primary City | Company |
|---|---|---|---|
| 240-246 | Montgomery | Gaithersburg, MD | Starpower Communications |
| 240-247 | Prince Georges | Mount Rainier, MD | Allegiance Telecom |
| 240-248 | Saint Marys | Ridge, MD | Peerless Network Of Maryland |
| 240-249 | Saint Marys | Mechanicsville, MD | Teleport Communications America - DC |
| 240-250 | Prince Georges | Brandywine, MD | Peerless Network Of Maryland |
| 240-251 | Washington | Highfield, MD | Core Communications |
| 240-252 | Montgomery | Gaithersburg, MD | Level 3 Communications |
| 240-253 | Prince Georges | Mount Rainier, MD | Global Crossing Local Services-md |
| 240-254 | Charles | Hughesville, MD | Teleport Communications America - DC |
| 240-255 | Montgomery | Poolesville, MD | Peerless Network Of Maryland |
| 240-256 | Saint Marys | Leonardtown, MD | Teleport Communications America - DC |
| 240-257 | Charles | Nanjemoy, MD | Teleport Communications America - DC |
| 240-258 | Saint Marys | Ridge, MD | Teleport Communications America - DC |
| 240-260 | Prince Georges | Mount Rainier, MD | Allegiance Telecom |
| 240-262 | Saint Marys | Callaway, MD | Sprint Spectrum L.p. |
| 240-263 | Montgomery | Bethesda, MD | Sprint Spectrum L.p. |
| 240-264 | Prince Georges | Beltsville, MD | Verizon Maryland |
| 240-265 | Montgomery | Bethesda, MD | Sprint Spectrum L.p. |
| 240-266 | Prince Georges | Mount Rainier, MD | Peerless Network Of Maryland |
| 240-268 | Montgomery | Rockville, MD | Allegiance Telecom |
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.