List of original NANP area codes

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This is the list of original North American Numbering Plan area codes of 86 plan areas as defined by AT&T in 1947.

In preparation for direct distance dialing, AT&T and the Bell System developed the North American Numbering Plan in the 1940s. The plan divided the United States and Canada into numbering plan areas (NPAs) and assigned a three-digit dialing prefix to each. Over the course of the decade following introduction of these routing codes, local subscriber numbers were standardized to seven digits. This included a three-digit central office prefix, dialed as the first two letters of the local exchange name and one digit, and the four-digit subscriber line number.

The original numbering plan defined the second digit of all area codes as either 0 or 1, to distinguish them from the local telephone exchange prefixes, which were assigned digits 2 through 9 in the second position. Area codes with a middle digit 0 (zero, ten dial pulses) were assigned to plan areas that covered an entire state or province, while jurisdictions with multiple plan areas received area codes having 1 (one, a single pulse) in the second digit.[1] This permitted long distance calls to be dialed within the same area code as a seven digit subscriber number without the area code.

The most prominent, frequently called population centers were assigned digit sequences with the shortest dial time on rotary dial telephones.[2] For example, New York City was assigned 212, Los Angeles 213, Chicago 312, and Detroit 313.

No codes of the form N00, N10 or N11 occur in the original set. The N00 series was used for non-geographic numbers, starting with intrastate toll-free +1-800 numbers in 1966.[3] N10 numbers were originally teletypewriter exchanges and N11 remains reserved for information and emergency numbers. No codes were originally assigned to Alaska and Hawaii (neither of which were US states at the time) or Puerto Rico.[4]

Initially, the codes were used only by long-distance operators; the first customer-dialed call using an area code was placed on November 10, 1951, from Englewood, New Jersey, to Alameda, California.[5] Direct dialing was gradually implemented throughout the continent and by the mid-1960s, direct distance dialing was commonplace in most larger cities.

Original area codes[edit]

See also[edit]