North American area coes 240 and 301 are state of Maryland telephone area codes which serve Maryland's portion of the Greater Washington, D.C. metro area, portions of Southern Maryland, and all points northwest of Washington. This includes the communities of Cumberland, Frederick, Hagerstown, and Gaithersburg. Area code 301 was one of the original area codes established in 1947, and was the exclusive area code for the entire state of Maryland until it was split to form 410 on October 6, 1991. The overlay area code, 240, was introduced on June 1, 1997.