| 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 |
|---|---|---|---|
| 240-912 | Gaithersburg | Montgomery | Landline |
| 240-903 | Indian Head | Charles | Landline |
| 240-237 | Callaway | Saint Marys | Landline |
| 240-895 | Patuxent River | Saint Marys | Landline |
| 240-214 | Charlotte Hall | Saint Marys | Landline |
| 240-545 | Upper Marlboro | Prince Georges | Landline |
| 240-778 | Bethesda | Montgomery | Landline |
| 240-280 | Laurel | Howard | Landline |
| 240-507 | Glen Echo | Montgomery | Wireless |
| 240-731 | Rockville | Montgomery | Wireless |
| 240-333 | Brentwood | Prince Georges | Landline |
| 240-674 | Frederick | Frederick | Wireless |
| 240-321 | Oakland | Garrett | Wireless |
| 240-772 | Frederick | Frederick | Wireless |
| 240-528 | Hughesville | Charles | Landline |
| 240-880 | Bethesda | Montgomery | Landline |
| 240-650 | Glen Echo | Montgomery | Landline |
| 240-291 | Hagerstown | Washington | Wireless |
| 240-355 | Laurel | Prince Georges | Wireless |
| 240-558 | Silver Spring | Montgomery | Landline |