Telephone Numbers in The United States - History

History

The North American Numbering Plan was developed in the 1940s in the Bell System serving the United States and Canada with an unorganized system of many differing numbering plans based on the needs of the individual local telephone operating companies. It was first implemented in 1951 with the introduction of direct distance dialing (DDD). Today, under an independent administration provided by Neustar (formerly Lockheed Martin IMS), the system has grown to include the United States and its territories, Canada, Bermuda, and 17 nations of the Caribbean. The term is also used, by metonymy, to refer to the geographic area in which that plan has been implemented.

For the introduction of direct customer dialing of long-distance telephone calls, the Bell System set out to unify the various numbering plans in existence at the time. Area code 201 was the first implemented under the plan.

At the request of the British Colonial Office, the numbering plan was first expanded to Bermuda and the British West Indies, including Trinidad and Tobago), because of their historic telecommunications administration through Canada as parts of the British Empire, and their continued associations with Canada, especially during the years of the telegraph and the All Red Line system.

Despite its name, not all North American countries participate in NANP. Mexico, the Central American countries and some Caribbean countries (Cuba, Haiti, and the French Caribbean are not part of the system. The only Spanish-speaking sovereign nation in this plan is the Dominican Republic. Mexican participation was planned, but implementation stopped after two area codes were put into use (Mexico City and northwestern Mexico); these ended in 1991 when Mexico withdrew from the NANP. Dutch-speaking Sint Maarten joined the NANP in September 2011.

Saint Pierre and Miquelon (+508) and Greenland (+299), both North American possessions of European Union nations, use non-NANP codes which are independent of their respective home countries (+33 France and +45 Denmark).

At first, area codes were used only by long-distance operators; the first customer-dialed calls using area codes occurred on November 10, 1951, when the first directly dialed call was made from Englewood, New Jersey to Alameda, California. Direct dialing was gradually instituted throughout the country, and by the mid-1960s, it was commonplace in cities and most larger towns.

Originally there were only 86 codes, with the biggest population areas getting the numbers that took the shortest time to dial on rotary telephones. Thus, five largest cities based on 1950 US Census population received some of the "shortest" codes: New York City was given 212, Chicago 312, Los Angeles 213, Detroit 313, Philadelphia 215; while four areas received the then-maximum number of 21 clicks: South Dakota (605), North Carolina (704), South Carolina (803), and the Maritime Provinces of Canada (902). Additionally, in the original plan a middle digit of 0 indicated that the area code covered an entire state/province, while area codes with a middle digit of 1 were assigned to jurisdictions that were divided into multiple area codes.

At first, area codes were all in the form NYX, where N is any number 2–9, Y is 0 or 1, and X is any number 1–9 (if Y is 0) or any number 2–9 (if Y is 1). The restriction on N saves 0 for calling the operator, and 1 for signaling a long-distance call. The restriction on the second digit, limiting it to 0 or 1, was designed to help telephone equipment recognize the difference between a three-digit "area code" (with 0 or 1 as the second digit) and the three-digit "exchange" prefix (which had avoided 0 or 1 for the second digit, because of restrictions in existing switching equipment). For example, when a caller dialed "202-555-1212", the switching equipment would recognize that "202" was an area code because of the middle 0, and route the call appropriately. If a caller were to dial 345-6789, the 4 would cause the number to be recognized as a long-distance number within the area and routed as such, without waiting for the caller to finish dialing.

In the late 1980s and early 1990s, NANPA (then still part of Bellcore, which is now Telcordia Technologies) began to urge and later require all long-distance calls within each area to be prefixed with the digit 1 to distinguish them from local calls, so that badly needed prefixes with 0 or 1 in the middle could be assigned to local telephone exchanges. Also, since it had nearly run out of area codes using the above formula, it allowed the assignment of area codes using the form N10, such as 210 in the San Antonio, Texas, area and 410 in eastern Maryland. Therefore, someone calling from San Jose to Los Angeles before the change would have dialed 213-555-1234 and after the change 1-213-555-1234, which then allowed 213 to be used as an exchange prefix in the San Jose area.

Until 1991, calls to some areas of Mexico from the United States and Canada were made using NANP area codes, but Mexican participation in the NANP was discontinued in favor of the general international format, using country code +52 instead. Area code 905 (formerly Mexico City) was re-assigned to a split of area code 416 (the Greater Toronto Area); area code 706 (formerly northwest Mexico) was reassigned to northern Georgia, surrounding the Atlanta region which retained 404; and area code 903, which also served a small portion of northern Mexico, was reclaimed and later reassigned to northeastern Texas when it split from area code 214.