| 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 |
|---|---|---|---|
| 240-319 | Columbia | Howard | Wireless |
| 240-329 | Hagerstown | Washington | Landline |
| 240-882 | District Heights | Prince Georges | Wireless |
| 240-567 | Rockville | Montgomery | Landline |
| 240-533 | Brentwood | Prince Georges | Landline |
| 240-638 | Brentwood | Prince Georges | Landline |
| 240-965 | Greenbelt | Prince Georges | Landline |
| 240-578 | Frederick | Frederick | Wireless |
| 240-938 | Ashton | Montgomery | Wireless |
| 240-408 | Rockville | Montgomery | Wireless |
| 240-463 | Silver Spring | Montgomery | Wireless |
| 240-671 | Brentwood | Prince Georges | Wireless |
| 240-575 | Frederick | Frederick | Landline |
| 240-367 | Frederick | Frederick | Wireless |
| 240-530 | Waldorf | Charles | Landline |
| 240-438 | Silver Spring | Montgomery | Wireless |
| 240-618 | Rockville | Montgomery | Wireless |
| 240-326 | Upper Marlboro | Prince Georges | Landline |
| 240-519 | Chevy Chase | Montgomery | Wireless |
| 240-422 | Frederick | Frederick | Wireless |