| 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 |
|---|---|---|---|
| 240-347 | Hagerstown | Washington | Landline |
| 240-489 | Poolesville | Montgomery | Landline |
| 240-743 | Glen Echo | Montgomery | Landline |
| 240-447 | Rockville | Montgomery | Wireless |
| 240-494 | Brentwood | Prince Georges | Landline |
| 240-288 | Thurmont | Frederick | Landline |
| 240-420 | Hagerstown | Washington | Landline |
| 240-433 | Rockville | Montgomery | Landline |
| 240-310 | Hagerstown | Washington | Wireless |
| 240-657 | Frederick | Frederick | Landline |
| 240-513 | Hagerstown | Washington | Wireless |
| 240-356 | Frederick | Frederick | Landline |
| 240-275 | Grantsville | Garrett | Landline |
| 240-375 | District Heights | Prince Georges | Wireless |
| 240-808 | Leonardtown | Saint Marys | Wireless |
| 240-993 | Indian Head | Charles | Landline |
| 240-716 | Brentwood | Prince Georges | Wireless |
| 240-220 | Poolesville | Montgomery | Landline |
| 240-556 | Bowie | Prince Georges | Landline |
| 240-580 | Cumberland | Allegany | Wireless |