| 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 |
|---|---|---|---|
| 240-964 | Cumberland | Allegany | Landline |
| 240-737 | Brentwood | Prince Georges | Landline |
| 240-281 | Chevy Chase | Montgomery | Wireless |
| 240-802 | Brentwood | Prince Georges | Wireless |
| 240-503 | Issue | Charles | Landline |
| 240-813 | Gaithersburg | Montgomery | Landline |
| 240-551 | Rockville | Montgomery | Wireless |
| 240-394 | Mount Airy | Frederick | Wireless |
| 240-593 | Laurel | Howard | Wireless |
| 240-456 | Laurel | Anne Arundel | Landline |
| 240-309 | Silver Spring | Montgomery | Wireless |
| 240-474 | Gaithersburg | Montgomery | Landline |
| 240-855 | Glen Echo | Montgomery | Wireless |
| 240-520 | Hagerstown | Washington | Wireless |
| 240-641 | Silver Spring | Montgomery | Wireless |
| 240-529 | Frederick | Frederick | Landline |
| 240-278 | Laurel | Howard | Wireless |
| 240-316 | Bethesda | Montgomery | Wireless |
| 240-246 | Gaithersburg | Montgomery | Landline |
| 240-392 | Brentwood | Prince Georges | Landline |