| District of Maryland area codes: 240 | |
|---|---|
| Country | United States |
| State/Province | Maryland |
| Major City | Baltimore |
| Time Zone | Eastern |
| Prefix | County | Primary City | Company |
|---|---|---|---|
| 240-223 | Prince Georges | Mount Rainier, MD | Allegiance Telecom |
| 240-224 | Montgomery | Gaithersburg, MD | Cellco Partnership DBA Verizon Wireless |
| 240-225 | Frederick | Frederick, MD | Core Communications |
| 240-228 | Prince Georges | Laurel, MD | Verizon Maryland |
| 240-229 | Charles | Waldorf, MD | Broadwing Communications. LLC |
| 240-230 | Charles | Hughesville, MD | Global Crossing Local Services-md |
| 240-231 | Washington | Hagerstown, MD | Core Communications |
| 240-232 | Prince Georges | Mount Rainier, MD | Broadwing Communications. LLC |
| 240-233 | Charles | Newburg, MD | Teleport Communications America - DC |
| 240-234 | Prince Georges | Mount Rainier, MD | Cellco Partnership DBA Verizon Wireless |
| 240-235 | Montgomery | Bethesda, MD | Paetec Communications |
| 240-236 | Frederick | Frederick, MD | Verizon Maryland |
| 240-237 | Saint Marys | Callaway, MD | Teleport Communications America - DC |
| 240-238 | Montgomery | Rockville, MD | Paetec Communications |
| 240-239 | Saint Marys | Leonardtown, MD | Core Communications |
| 240-241 | Montgomery | Chevy Chase, MD | Starpower Communications |
| 240-242 | Montgomery | Kensington, MD | Starpower Communications |
| 240-243 | Montgomery | Gaithersburg, MD | Allegiance Telecom |
| 240-244 | Prince Georges | Mount Rainier, MD | Starpower Communications |
| 240-245 | Prince Georges | Glenn Dale, MD | Starpower Communications |
There are 522 prefixes, In the code area, the major cities are Aspen Hill, MD;Bethesda, MD;Bowie, MD;Chillum, MD;. The major city is Baltimore.