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# What is the history of the U.S. area code?

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Use of areas codes in the United States began in 1947. Developed by AT&T and Bell Labs for the U.S. and Canada, the system is called North American Numbering Plan (NANP) and it governs how cities and states are assigned area codes.

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The first area code in the U.S. was 201, issued to New Jersey in 1951. It established one protocol for assigning area codes-–that high-population areas got the codes with the lowest numbers. For instance, 201 is easier to dial on a rotary dial phone than 901, which could be for a suburban or rural area. The rationale was that since more people used phones in the cities than in the country, city dwellers should work less to dial.

The formula to generate are codes uses values NYX, where N equals any numeral 2 to 9, Y equals 0 or 1 and X is any number 1 through 9 unless Y is 1, which restricts the values for X to 2 through 9. Though this formula generates 152 possible codes, only 86 have been assigned, as of 2015. Area codes with 0 as the second digit are assigned to an entire state, while area codes with the second digit as 1 signifies that the state or city has more than one code. Because the system had run out of area codes by the 1980s, the North American Numbering Plan Administration implemented new protocols for area codes that allow freer use of 0 to increase the pool of numbers.

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