301, 240 & 227 Area Codes
301, 240, and 227 area codes are Maryland area codes covering the area surrounding Washington D.C.; it covers the southwestern and northwestern parts of Maryland. Area code 301 was one of the original area code created in 1947 and was the only area code in Maryland until October 6th, 1991. In 1991, when area code 301 was split, 410 area code was formed. Due to the high demand and more residents moving into Maryland, 240 area code was introduce on June 1st, 1997 to overlaid with 301 area code
| Abell, MD | Accident, MD | Accokeek, MD |
| Adamstown, MD | Andrews Afb, MD | Aquasco, MD |
| Ashton, MD | Avenue, MD | Barnesville, MD |
| Barton, MD | Beallsville, MD | Bel Alton, MD |
| Beltsville, MD | Benedict, MD | Bethesda, MD |
| Big Pool, MD | Bittinger, MD | Bladensburg, MD |
| Bloomington, MD | Boonsboro, MD | Bowie, MD |
| Boyds, MD | Braddock Heights, MD | Brandywine, MD |
| Brentwood, MD | Brinklow, MD | Brookeville, MD |
| Brownsville, MD | Brunswick, MD | Bryans Road, MD |
| Bryantown, MD | Buckeystown, MD | Burkittsville, MD |
| Burtonsville, MD | Bushwood, MD | Cabin John, MD |
| California, MD | Callaway, MD | Capitol Heights, MD |
| Cascade, MD | Cavetown, MD | Chaptico, MD |
| Charlotte Hall, MD | Cheltenham, MD | Chevy Chase, MD |
| Chewsville, MD | Clarksburg, MD | Clear Spring, MD |
| Clements, MD | Clinton, MD | Cobb Island, MD |
| College Park, MD | Coltons Point, MD | Compton, MD |
| Corriganville, MD | Cumberland, MD | Damascus, MD |
| Dameron, MD | Derwood, MD | Dickerson, MD |
| District Heights, MD | Drayden, MD | Eckhart Mines, MD |
| Ellerslie, MD | Emmitsburg, MD | Fairplay, MD |
| Faulkner, MD | Flintstone, MD | Fort Washington, MD |
| Frederick, MD | Friendship, MD | Friendsville, MD |
| Frostburg, MD | Funkstown, MD | Gaithersburg, MD |
| Garrett Park, MD | Germantown, MD | Glen Echo, MD |
| Glenn Dale, MD | Grantsville, MD | Great Mills, MD |
| Greenbelt, MD | Hagerstown, MD | Hancock, MD |
| Helen, MD | Highland, MD | Hollywood, MD |
| Hughesville, MD | Hyattsville, MD | Ijamsville, MD |
| Indian Head, MD | Ironsides, MD | Issue, MD |
| Jefferson, MD | Keedysville, MD | Kensington, MD |
| Kitzmiller, MD | Knoxville, MD | La Plata, MD |
| Ladiesburg, MD | Lanham, MD | Laurel, MD |
| Laurel, MD | Laurel, MD | Leonardtown, MD |
| Lexington Park, MD | Libertytown, MD | Little Orleans, MD |
| Lonaconing, MD | Loveville, MD | Luke, MD |
| Marbury, MD | Maugansville, MD | Mc Henry, MD |
| Mechanicsville, MD | Middletown, MD | Midland, MD |
| Midlothian, MD | Monrovia, MD | Montgomery Village, MD |
| Morganza, MD | Mount Airy, MD | Mount Rainier, MD |
| Mount Savage, MD | Mount Victoria, MD | Myersville, MD |
| Nanjemoy, MD | New Market, MD | New Midway, MD |
| Newburg, MD | Oakland, MD | Oldtown, MD |
| Olney, MD | Owings, MD | Oxon Hill, MD |
| Park Hall, MD | Patuxent River, MD | Piney Point, MD |
| Pinto, MD | Point Of Rocks, MD | Pomfret, MD |
| Poolesville, MD | Port Tobacco, MD | Potomac, MD |
| Rawlings, MD | Ridge, MD | Riverdale, MD |
| Rock Point, MD | Rockville, MD | Rocky Ridge, MD |
| Rohrersville, MD | Sabillasville, MD | Saint Inigoes, MD |
| Saint James, MD | Saint Marys City, MD | Sandy Spring, MD |
| Scotland, MD | Sharpsburg, MD | Silver Spring, MD |
| Smithsburg, MD | Southern MD Facility, MD | Spencerville, MD |
| Spring Gap, MD | Suburb Maryland Fac, MD | Suitland, MD |
| Swanton, MD | Takoma Park, MD | Tall Timbers, MD |
| Temple Hills, MD | Thurmont, MD | Tuscarora, MD |
| Unionville, MD | Upper Marlboro, MD | Valley Lee, MD |
| Waldorf, MD | Walkersville, MD | Washington, DC |
| Washington Grove, MD | Welcome, MD | Westernport, MD |
| White Plains, MD | Williamsport, MD | Woodsboro, MD |