what area code is 301

The area code 301 is located in western Maryland and covers Germantown, Silver Spring, Waldorf, Frederick, and Rockville. It is part of the North American Numbering Plan (NANP) for the western part of the U.S. state of Maryland, along with area codes 240 and 227. The 301 area code was the first area code for all of Maryland, from 1947 until 1991, when the NPA was reduced in geographic extent. In 1997, it was converted to an overlay numbering plan with the addition of the second area code 240. On June 14, 2023, a third overlay code, 227, was added to provide more central office prefixes for new telephone numbers. The 301 area code covers Western Maryland, specifically the part of Maryland that is included in the Washington DC metro area.