Area codes 201 and 551 are telephone area codes in the North American Numbering Plan (NANP) 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 formed. After splits in 1957, 1991 and 1997, it is assigned to the northeasternmost portion of the state, including most of Hudson and Bergen counties on the Hudson River, bordering New York City. Major cities in the numbering plan area include Bayonne, Jersey City, Hoboken, Hackensack, Secaucus and Englewood. Area code 551 was added to this numbering plan area in 2001 in formation of an overlay. History Area code 201 was the first-assigned numbering plan area (NPA) code of the original 86 area codes when the American Telephone and Telegraph Company (AT&T) devised the nationwide 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 was originally assigned to the entire state of New Jersey, despite the state's dense population, the highest in the nation. The bulk of New Jersey's population is concentrated in the large metropolitan area west of New York City in the northeast and the suburbs of Philadelphia in the southwest. The geographic coverage of numbering plan areas was based on several criteria. A numbering plan area could for technical reason related to the numbering plan only have a maximum of 540 central offices; larger states needed to be divided. In addition, the call routing infrastructure had to be suitable to be centrally coordinated by only one toll center without expensive back-haul arrangements. For the latter reason, by 1956, 201 was reduced to northern New Jersey, while the area from the state capital, Trenton, southward, including the southern Jersey Shore and the New Jersey side of the lower Delaware Valley, received area code 609. This separated the two population centers into distinct call routing administrations. Despite the division with two area codes, all calls within the state of New Jersey were dialed without area codes until July 21, 1963, when office code protection was ended. For over thirty years, area code 201 served Bergen, Hudson, Ocean, Essex, Union, Morris, Passaic, Hunterdon, Somerset, Middlesex, Monmouth, Sussex and Warren counties. As the central region