| 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 |
|---|---|---|---|
| 240-783 | Chevy Chase | Montgomery | Wireless |
| 240-260 | Brentwood | Prince Georges | Landline |
| 240-439 | Frederick | Frederick | Wireless |
| 240-245 | Bowie | Prince Georges | Landline |
| 240-357 | Frederick | Frederick | Wireless |
| 240-536 | Ashton | Montgomery | Landline |
| 240-358 | Clarksburg | Montgomery | Landline |
| 240-430 | Silver Spring | Montgomery | Landline |
| 240-777 | Rockville | Montgomery | Landline |
| 240-213 | Waldorf | Charles | Landline |
| 240-448 | Waldorf | Charles | Wireless |
| 240-344 | Frederick | Frederick | Wireless |
| 240-452 | Hagerstown | Washington | Landline |
| 240-685 | Cheltenham | Prince Georges | Landline |
| 240-893 | Silver Spring | Montgomery | Wireless |
| 240-287 | Hancock | Washington | Landline |
| 240-625 | Hagerstown | Washington | Wireless |
| 240-305 | Laurel | Prince Georges | Wireless |
| 240-228 | Laurel | Anne Arundel | Landline |
| 240-899 | Chevy Chase | Montgomery | Wireless |