| District of Maryland area codes: 240 | |
|---|---|
| Country | United States |
| State/Province | Maryland |
| Major City | Baltimore |
| Time Zone | Eastern |
| Prefix | County | Primary City | Company |
|---|---|---|---|
| 240-392 | Prince Georges | Oxon Hill, MD | Starpower Communications |
| 240-393 | Montgomery | Cabin John, MD | Cellco Partnership DBA Verizon Wireless |
| 240-394 | Carroll | Mount Airy, MD | New Cingular Wireless PCS - DC |
| 240-395 | Montgomery | Bethesda, MD | Cavalier Telephone Mid-atlantic |
| 240-396 | Prince Georges | Mount Rainier, MD | Global Crossing Local Services-md |
| 240-397 | Frederick | Frederick, MD | Cellco Partnership DBA Verizon Wireless |
| 240-398 | Montgomery | Cabin John, MD | Sprint Spectrum L.p. |
| 240-399 | Montgomery | Chevy Chase, MD | Xo Maryland |
| 240-400 | Montgomery | Bethesda, MD | Sprint Spectrum L.p. |
| 240-401 | Montgomery | Rockville, MD | New Cingular Wireless PCS - DC |
| 240-402 | Prince Georges | College Park, MD | Mci Worldcom Communications |
| 240-403 | Montgomery | Rockville, MD | Cavalier Telephone Mid-atlantic |
| 240-404 | Montgomery | Gaithersburg, MD | Xo Maryland |
| 240-405 | Frederick | Frederick, MD | Us Lec Of Maryland |
| 240-406 | Montgomery | Rockville, MD | Leap Wireless Intl DBA Cricket Comm |
| 240-407 | Prince Georges | Mount Rainier, MD | Global Crossing Local Services-md |
| 240-408 | Montgomery | Rockville, MD | Leap Wireless Intl DBA Cricket Comm |
| 240-409 | Frederick | Frederick, MD | New Cingular Wireless PCS - DC |
| 240-412 | Charles | Waldorf, MD | Sprint Spectrum L.p. |
| 240-413 | Prince Georges | Hyattsville, MD | Omnipoint Communications Cap Operations |
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.