| General Information about Area Code 240 | |
|---|---|
| Country | United States |
| State / Province / Territory | Maryland |
| Major City | Gaithersburg |
| Time Zone | Eastern (UTC-05:00) |
| Prefix | Primary City | County | Phone Type |
|---|---|---|---|
| 240-421 | Rockville | Montgomery | Wireless |
| 240-387 | Bethesda | Montgomery | Landline |
| 240-225 | Frederick | Frederick | Landline |
| 240-242 | Bethesda | Montgomery | Landline |
| 240-524 | Laurel | Howard | Landline |
| 240-373 | Odenton | Anne Arundel | Landline |
| 240-770 | Brentwood | Prince Georges | Landline |
| 240-762 | Brentwood | Prince Georges | Wireless |
| 240-816 | - | - | - |
| 240-617 | Hagerstown | Washington | Landline |
| 240-384 | Callaway | Saint Marys | Landline |
| 240-901 | Port Tobacco | Charles | Landline |
| 240-409 | Frederick | Frederick | Wireless |
| 240-595 | Bethesda | Montgomery | Wireless |
| 240-505 | Silver Spring | Montgomery | Wireless |
| 240-440 | Frederick | Frederick | Wireless |
| 240-548 | Brentwood | Prince Georges | Landline |
| 240-264 | Laurel | Prince Georges | Landline |
| 240-471 | Rockville | Montgomery | Landline |
| 240-403 | Rockville | Montgomery | Landline |