History of US Area Codes

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Remarkably, there is some very logical reasoning behind US area codes. In the 1940s, the Bell System needed to modify the complicated system using operators to process long-distance telephone calls. Therefore, Bell created the North American Numbering Plan (NANP) to permit automated long-distance dialing. NANP created 86 Numbering Plan Areas (NPAs) or US area codes in North America.

Thirty-four states and the District of Columbia had one US area code. Three Canadian provinces shared a single area code, and New York State had five US area codes. Any state with a single or shared US area code had a zero as a middle digit. For example, New Jersey’s US area code was 201. Multi-code states had a one as their middle digit, like 212 for New York. Since telephones used rotary dials, high population states had smaller “dial pulls” than low population states. Therefore, New York State (US area code 212) had fewer dial pulls than Indiana (812) or Minnesota (218), both lower population states.

North American Numbering Plan Administration

After the breakup of the Bell System, the Federal Communications Commission (FCC) established the North American Numbering Plan Administration (NANPA) in the United States. A private sector company operates NANPA under an FCC contract. Currently, the NANP is the numbering plan for area codes in the US, its territories, Canada, and some Caribbean countries.

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NANPA is responsible for neutral administration, not regulatory authority, of the NANP. It assigns US area codes and coordinates planning, data collection, and forecasting. In the US, the NANPA follows FCC regulations and industry-developed guidelines.

NANPA Services

The services provided by NANPA include code administration, NPA relief planning, Numbering Resource Utilization/ Forecast (NRUF) data collection and analysis, and NANPA enterprise services.

Code Administration – Code administration work includes providing information about numbering resources, processing resource applications, assigning numbering resources, advising regulators and industry about resource exhaustion, and reclaiming unused resources.

NPA Relief Planning – NPA relief planning includes estimating when numbers in each US area code will be depleted, convening industry meetings to discuss alternative NPA supply methods, helping the industry to achieve consensus, submitting plans for state approvals, publishing relief plans, and assisting implementation of new plans.

NRUF Data Collection and Analysis – According to FCC regulations, assignees holding certain telephone numbers must report their holdings twice a year. NANPA must collect, store, and maintain this data.
NANPA Enterprise Services – These are additional services for a specific NANPA fee. They include rating and routing data, paper submissions of resource applications, entry of paper NRUF submissions, testimony in regulatory hearings, and customized reports.

NANPA Numbering Resources

The NANPA Numbering Resources web page has links for US area code searches, searches of US area codes for cities or towns greater than 20,000 people, and area code maps. There is also a link for planned area codes not yet in service. There are also links for other plans and reports.

US area codes use three-digit NPA codes with a format of NXX. N is any digit “2” through “9” while X stands for any digit “0” through “9”. There are 800 possible area code combinations in the NANP plan. “N11” codes are not area codes. They are service codes. The 80 “N9X” format codes are expansion codes. The Industry Numbering Committee (INC) has set aside two blocks of 10 codes (37X and 96X) for unanticipated purposes.

Central Office Codes

Central office codes follow the format NXX, and they are digits four, five, and six of a ten-digit phone number. Central office codes define the exchange related to state-authorized service providers. NANPA assigns these codes.

N11 Codes

These codes are not area codes. They provide access to special services. In the United States, the FCC administers the N11 codes. A list of N11 codes follows:

  • 211 – Community Information and Referral Services
  • 311 – Non-Emergency Police and Other Governmental Services
  • 411 – Local Directory Information
  • 511 – Traffic and Transportation Information (US)
  • 611 – Repair Service
  • 711 – Telecommunications Relay Service
  • 811 – Protections of Pipeline and Utilities from Excavation (US)
  • 911 – Emergency
5XX-NXX-XXXX Assignments

These numbers using the 5XX US area code are reserved for non-geographic applications. NANPA assigns blocks of 10,000 numbers using this format to service providers to communicate with fixed and mobile devices.

900-NXX-XXXX Assignments

The “900” US area code is used for premium services. The calling party is billed for each “900” call. Service providers receive blocks of 10,000 numbers, and bill callers for these premium services. The 900 numbers are not portable.

456-NXX Codes

In 1993, 456 area code numbers identified carrier-specific services. However, in 2017, the INC determined there was no need for these numbers. They sunsetted the 456 area code numbers for five years before returning them to general use.

555 Line Numbers

Starting in 1994, a variety of information services used 555 numbers with any US area codes. However, all 555 line numbers are now part of NANPA resources. Two 555 numbers remain in use: 555-1212 for national directory assistance and 555-4334 for assigned national use. Entertainment and advertising use fictitious 555-0100 through 555-0199 non-working numbers.
800-855-XXXX Line Numbers

Services, for the deaf, hard of hearing, or speech impaired, use 800-855-XXXX line numbers. Public switched telephone networks facilitate telecommunications relay services and message relay services. This link gives current 800-855-XXXX number assignments.