Maryland Area Code Information
(301 and 240) - (410 and 443 and 667)
Maryland is currently using five area codes. Maryland is utilizing two area code overlay plans, often called overlay complexes.
Maryland originally had one area code, 301, when the numbering system was established in 1947. It was not until forty-four years later in 1991 that Maryland experienced sufficient growth in population and telephone use to need an additional area code. To meet this increase in demand area code 301 was split to form area code 410. Later in 1997 area code 301 was overlaid with area code 240 and area code 410 was overlaid with area code 443. These changes resulted in four area codes being utilized in Maryland by 1997. In 2012 Maryland added area code 667 as an overlay of area codes 410/443/667.
Changes and History of Maryland Area Codes:
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.
Area code 410 was put into service. Area code 410 was created from a split of area code 301. In 1997 area code 410 was overlaid with area code 443.
Area code 240 was put into service. Area code 240 is an overlay of area code 301.
Area code 443 was put into service. Area code 443 is an overlay of area code 410.
Area code 667 was put into service as an overlay of area code 443 and 410. The new overlay plan is 410/443/667.
not in service
Area code 227 is proposed as an overlay of area code 240 and 301 but is not yet in service. When area code 227 is implemented the new overlay plan, or complex, will be 301/240/227.