| 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 |
|---|---|---|---|
| 240-532 | Brentwood | Prince Georges | Wireless |
| 240-248 | Ridge | Saint Marys | Landline |
| 240-441 | Temple Hills | Prince Georges | Wireless |
| 240-369 | Mount Airy | Frederick | Landline |
| 240-351 | Laurel | Prince Georges | Wireless |
| 240-669 | Brentwood | Prince Georges | Landline |
| 240-613 | Brentwood | Prince Georges | Landline |
| 240-464 | Chevy Chase | Montgomery | Landline |
| 240-577 | Leonardtown | Saint Marys | Wireless |
| 240-976 | - | - | - |
| 240-435 | Waldorf | Charles | Wireless |
| 240-818 | Smithsburg | Washington | Landline |
| 240-612 | Brentwood | Prince Georges | Landline |
| 240-324 | Highland | Howard | Landline |
| 240-754 | Waldorf | Charles | Landline |
| 240-504 | Silver Spring | Montgomery | Wireless |
| 240-848 | Gaithersburg | Montgomery | Wireless |
| 240-461 | Silver Spring | Montgomery | Wireless |
| 240-476 | Silver Spring | Montgomery | Wireless |
| 240-490 | Middletown | Frederick | Wireless |