| 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 |
|---|---|---|---|
| 240-427 | Waldorf | Charles | Landline |
| 240-399 | Bethesda | Montgomery | Landline |
| 240-204 | Chevy Chase | Montgomery | Wireless |
| 240-343 | Hancock | Washington | Wireless |
| 240-839 | Bethesda | Montgomery | Wireless |
| 240-543 | Chevy Chase | Montgomery | Wireless |
| 240-793 | Gaithersburg | Montgomery | Wireless |
| 240-892 | Upper Marlboro | Prince Georges | Landline |
| 240-675 | Myersville | Frederick | Wireless |
| 240-863 | Laurel | Prince Georges | Landline |
| 240-431 | Great Mills | Saint Marys | Wireless |
| 240-573 | Cheltenham | Prince Georges | Landline |
| 240-252 | Gaithersburg | Montgomery | Landline |
| 240-687 | Silver Spring | Montgomery | Wireless |
| 240-236 | Frederick | Frederick | Landline |
| 240-360 | Laurel | Howard | Wireless |
| 240-460 | Silver Spring | Montgomery | Wireless |
| 240-295 | Laurel | Howard | Landline |
| 240-388 | Gaithersburg | Montgomery | Wireless |
| 240-614 | Rockville | Montgomery | Wireless |