Area Code 301 History:
Area code 301 was put into service. In 1991 area code 301 was split to form area code 410. In 1997 area codes 301 was overlaid with area code 240.
Counties in Maryland within area code 301 include:
Allegany County, Anne Arundel County, Calvert County, Charles County, Frederick County, Garrett County, Howard County, Montgomery County, Prince Georges County, Saint Marys County, and Washington County.
Major cities or places in Maryland within area code 301 include:
Area codes 240 and 301 serve central and western Maryland including Bethesda, College Park, Frederick, Gaithersburg, Hagerstown, Landover, Rockville, Silver Springs and Weaton-Glenmont in addition to many smaller communities northwest of Washington, D.C.