| 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 |
|---|---|---|---|
| 240-821 | Silver Spring | Montgomery | Landline |
| 240-784 | Myersville | Frederick | Wireless |
| 240-255 | Poolesville | Montgomery | Landline |
| 240-349 | Port Tobacco | Charles | Landline |
| 240-713 | Laurel | Howard | Landline |
| 240-437 | Ashton | Montgomery | Landline |
| 240-292 | Silver Spring | Montgomery | Landline |
| 240-646 | Laurel | Howard | Landline |
| 240-615 | Brentwood | Prince Georges | Wireless |
| 240-686 | Gaithersburg | Montgomery | Landline |
| 240-986 | Nanjemoy | Charles | Landline |
| 240-561 | Leonardtown | Saint Marys | Wireless |
| 240-718 | Callaway | Saint Marys | Landline |
| 240-327 | Gaithersburg | Montgomery | Landline |
| 240-336 | Chevy Chase | Montgomery | Landline |
| 240-487 | Brentwood | Prince Georges | Landline |
| 240-600 | Brentwood | Prince Georges | Wireless |
| 240-481 | Silver Spring | Montgomery | Wireless |
| 240-479 | Fort Washington | Prince Georges | Wireless |
| 240-832 | Chevy Chase | Montgomery | Wireless |