Area codes 201 and 551

Area codes 201 and 551 are telephone area codes in the North American Numbering Plan in the U.S. state of New Jersey. Area code 201 was the area code assigned to the entire state of New Jersey in 1947, when the North American area code system was formulated. After splits in 1958 and 1991, it covers the area of most of Hudson and Bergen counties. Major cities in the numbering plan area include Bayonne, Jersey City, Hoboken, Hackensack, Secaucus and Englewood. Area code 551 is an overlay code to the same numbering plan area that was installed in 2001.

Area code 201 was the first-assigned numbering plan area (NPA) code of the original NPAs when AT&T devised the North American Numbering Plan in 1947. It was also the first area code with Direct Distance Dialing (DDD) service, when in 1951 the first direct-dialed long-distance call was made from Englewood, New Jersey to Alameda, California.

Area code 201 originally covered the entire state of New Jersey, despite the state's dense population. The bulk of New Jersey's population is concentrated in the large metropolitan suburbs of New York City in the northeast and the suburbs of Philadelphia in the southwest. The creation of numbering plan areas was based on the anticipated number of central offices needed in each area and one plan area could only accommodate slightly over 500 central offices.

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