Nanpa

The North American Numbering Plan (NANP) is a telephone numbering plan that encompasses 25 distinct regions in twenty countries primarily in North America, including the Caribbean and the U.S. territories. Not all North American countries participate in the NANP.

The NANP was originally devised in the 1940s by AT&T for the Bell System and independent telephone operators in North America, to unify the diverse local numbering plans that had been established in the preceding decades. AT&T continued to administer the numbering plan until the breakup of the Bell System when administration was delegated to the North American Numbering Plan Administration (NANPA), a service that has been procured from the private sector by the Federal Communications Commission (FCC) in the United States. Each participating country forms a regulatory authority that has plenary control over local numbering resources. The FCC also serves as the U.S. regulator. Canadian numbering decisions are made by the Canadian Numbering Administration Consortium.

The NANP divides the territories of its members into numbering plan areas (NPAs) which are encoded numerically with a three-digit telephone number prefix, commonly called the area code. Each telephone is assigned a seven-digit telephone number unique only within its respective plan area. The telephone number consists of a three-digit central office code and a four-digit station number. The combination of an area code and the telephone number serves as a destination routing address in the public switched telephone network (PSTN). For international call routing, the NANP has been assigned the international calling code 1 by the International Telecommunications Union (ITU). The North American Numbering Plan conforms with ITU Recommendation E.164, which establishes an international numbering framework.

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