| District of Maryland area codes: 240 | |
|---|---|
| Country | United States |
| State/Province | Maryland |
| Major City | Baltimore |
| Time Zone | Eastern |
| Prefix | County | Primary City | Company |
|---|---|---|---|
| 240-352 | Charles | La Plata, MD | Peerless Network Of Maryland |
| 240-353 | Prince Georges | Beltsville, MD | Sprint Spectrum L.p. |
| 240-354 | Prince Georges | Beltsville, MD | Sprint Spectrum L.p. |
| 240-355 | Prince Georges | Beltsville, MD | Sprint Spectrum L.p. |
| 240-356 | Frederick | Frederick, MD | Level 3 Communications |
| 240-357 | Frederick | Frederick, MD | Cellco Partnership DBA Verizon Wireless |
| 240-358 | Montgomery | Damascus, MD | Peerless Network Of Maryland |
| 240-359 | Charles | Indian Head, MD | Peerless Network Of Maryland |
| 240-360 | Prince Georges | Laurel, MD | Omnipoint Communications Cap Operations |
| 240-361 | Montgomery | Gaithersburg, MD | Cavalier Telephone Mid-atlantic |
| 240-362 | Allegany | Cumberland, MD | Verizon Maryland |
| 240-363 | Montgomery | Kensington, MD | Global Naps South |
| 240-364 | Montgomery | Gaithersburg, MD | Cavalier East LLC |
| 240-365 | Montgomery | Damascus, MD | Baltimore-washington Telephone (bwt) |
| 240-366 | Washington | Williamsport, MD | AT&T Local |
| 240-367 | Frederick | Frederick, MD | Sprint Spectrum L.p. |
| 240-368 | Charles | Waldorf, MD | Peerless Network Of Maryland |
| 240-369 | Carroll | Mount Airy, MD | Core Communications |
| 240-370 | Montgomery | Bethesda, MD | Sprint Spectrum L.p. |
| 240-371 | Prince Georges | Mount Rainier, MD | Peerless Network Of Maryland |
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.