Telephone Numbers in The United States - Expansion

Expansion

Canada and the United States have experienced rapid growth in the number of area codes, particularly between 1990 and 2005. There are two main reasons for this. First, there is the increasing demand for telephone services (particularly resulting from widescale adoption of fax, modem, and mobile phone communications).

The second and more important reason is the telecom deregulation of local telephone service in the US beginning in the early to mid-1990s. At that time, the Federal Communications Commission began allowing telecommunication companies to compete with the incumbent local exchange carrier (usually by forcing the existing monopoly service provider to lease infrastructure to other local providers who then resold the service to consumers). However, because of the original design of the numbering plan and telephone switching network that assumed only a single provider, number allocations had to be made in 10,000-number blocks.

Thus, whenever a new local service provider entered a given market, it would be allocated 10,000 numbers by default, even if the provider only obtained a few customers. As more companies began requesting numbering allocations, this caused many area codes to begin exhausting their supply of available numbers (code "in jeopardy" in telecom jargon), and additional area codes were needed. In reality, many of the new telecom ventures were not successful; while the number of area codes started increasing rapidly, this did not necessarily translate to a much larger number of actual telephone subscribers as large blocks of numbers lay unassigned to any "real" subscribers because of the 10,000-number block allocation requirement. When these telecom ventures were merged or bought or liquidated, their blocks went to the successor or went unused. No regulatory mechanism existed to reclaim and reassign these underutilized blocks.

In general, area codes were added either as "splits" (in which an area code was divided into two or more regions, one retaining the older area code and the other area(s) receiving a new code), or "overlays", in which multiple codes are assigned to the same geographical area. Subtle variations of these techniques have been used as well, such as "dedicated overlays", in which the new overlaid code was reserved for a particular type of service, such as cellular phones and pagers (the only true example of this was area code 917 in New York City), and "concentrated overlays", in which a part of the area retained a single code while the rest of the region received an overlay code.

Area codes of the form N10, originally reserved for AT&T's Teletypewriter eXchange service, were transferred to Western Union in 1969 and were freed up other use in 1981 after conversion to Telex II service was complete. These eight "new" area codes were used for telephone area code splits in the late 1980s and early 1990s, as all other area codes under the original plan had been consumed.

After the remaining valid area codes were used up by expansion, in 1995 the rapid increase in the need for more area codes (both splits and overlays) forced NANPA to allow the digits 2 through 8 to be used as a middle digit in new area code assignments, with 9 being reserved as a "last resort" for potential future expansion. At the same time, local exchanges were allowed to use 1 or 0 as a middle digit. The first area codes without a 1 or 0 as the middle digit were area code 334 in Alabama and area code 360 in Washington, which both began service on January 15, 1995. This was quickly followed by area code 520 serving Arizona on March 19, 1995.

Codes ending in double digits are reserved as easily recognizable codes (ERCs), to be used for special purposes such as toll-free 800, 888, 877, 866 and 855, personal 700 numbers, and high-toll 900 numbers, rather than for geographic areas. (Nevada was denied 777 for this reason; it received 775 instead when most of Nevada split from 702, which continues to serve the Las Vegas metropolitan area.)