Original North American area codes

The original North American area codes were established by the American Telephone and Telegraph Company (AT&T) in 1947, after the demonstration of regional Operator Toll Dialing during the World War II period. The program had the goal of speeding the connecting times for long-distance calling by eliminating intermediary telephone operators. Expanding this technology for national use required a comprehensive and universal, continent-wide telephone numbering plan.

The new numbering plan established a uniform destination addressing and call routing system for all telephone networks in North America which had become an essential public service.^[1] It had the eventual benefit of direct distance dialing (DDD) by telephone subscribers, a feature by which a caller may, without operator assistance, call any other user outside the local calling area (typically requiring extra digits to be dialed).

The initial Nationwide Numbering Plan of 1947 established eighty-six numbering plan areas (NPAs) that conformed mainly to existing U.S. state and Canadian provincial boundaries, though fifteen states and provinces were subdivided further. Forty NPAs were mapped to entire states or provinces. Each NPA was identified by a three-digit area code used as a prefix to each local telephone number. The United States received seventy-seven area codes, and Canada nine. The initial system of numbering plan areas and area codes was expanded rapidly during the ensuing decades, and established the North American Numbering Plan (NANP).