How are telephone area codes determined?


Quick Answer

Telephone area codes are assigned by geographic location, with the exception of codes for toll-free dialing or for routing calls from outside North America. The United States has more than 310 area codes based on location. A few states only have one code, while larger states have several.

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Full Answer

The area code system for the United States and Canada was developed in the 1940s by AT&T and Bell Laboratories and was known as the North American Numbering Plan. The plan went into effect in 1947. At that time, there were 86 three-digit area codes. States and provinces assigned one code had a zero as the middle number. Parts of heavily populated California and New York had more than one area code, with the number one in the middle and the lowest number went to the most populated region. For example, New York City's code was 212 and the surrounding suburbs was 914. Since telephones were rotary dial, lower numbers had less dial pull and it took less time to make a call. Today, some parts of the United States have split codes within a geographic area. The Federal Communications Commission gives states authority to decide when to issue new area codes.

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