The first telephones had no numbers at all. Telephones were sold in pairs, and one caller would turn a crank to generate electricity to ring a bell at the other end. As the number of telephones in use increased, the existing telegraph system was modified to accommodate them, and operators began to connect callers.
During a measles outbreak in Lowell, MA, circa 1879, Dr. Moses Greeley Parker suggested that the town’s 200 subscribers be issued numbers to identify them. This would make it easier to train new operators if all the existing operators fell ill simultaneously. The earliest iterations of telephones had the numbers 2 - 9 on a dial with each digit assigned 3 letters, with the exception of Q and Z.
What are Alphanumeric Phone Numbers?
Telephone exchanges, also known as central offices, were regional hubs through which phone calls were routed. A telephone exchange identified the switching system to which a telephone was connected. Each exchange served a maximum of 10,000 subscriber lines, each identified by a unique last four digits. Areas or cities with more subscribers were served by multiple exchanges. The leading letters of an exchange name were used as the leading components of the telephone number and were mapped to digits on telephone dials.
The widely used numbering plan at the time was a system of using two letters from a central office name with four or five digits. It was designated as 2L-4N or 2L-5N, with L standing for “letters” and N for “numbers.” Initially, some cities used a 3L-4N or 2L-3N combination, but numbers were standardized to the 2L-5N combinations in the 1950s. An example is the Murray Hill 5-9975 telephone number. Murray Hill is a neighborhood in Manhattan, NY, and this number is actually 685-9975, with the 68, or “MU,” representing the “MUrray Hill” telephone exchange.
What is the North American Numbering Plan?
The need to resolve the complexities involved in making long-distance phone calls led to the creation of the North American Numbering Plan (NANP) in the 1940s. The Bell System evolved from the numerous local and regional telephone exchanges that arose in the different service territories. However, as the number of subscriber bases and service areas increased, the system developed into an unorganized collection of incompatible local numbering systems. This disorganization impeded efficient operation and interconnection of the exchanges into a nationwide system that facilitated long-distance calling.
This inefficiency spurred the Bell System to create a unified systemic approach to telephone call routing to simplify efficient long-distance calling. A new nationwide plan was introduced in October 1947, which divided the service territories into 86 numbering plan areas (NPAs). Each NPA was assigned a unique three-digit numeric numbering plan area code, colloquially referred to as an area code. These codes were used by long-distance operators to establish connections between the distant toll offices. The first customer-dialed direct call using area codes was placed on 10 November 1951 from Englewood, NJ, to Alameda, CA. This phone call officially introduced Direct Distance Dialling (DDD) across the country. By 1967, the number of NPAs had expanded to 129, and the system was named the North American Integrated Network to reflect the status of the network. This name was changed to the North American Numbering Plan in 1975 as other countries sought to join in the standardization.
The NANP is administered by the NANP Administrator and has been overseen by the Federal Communications Commission (FCC) since the breakup of the Bell System in 1984. The NANP Administrator is contracted by the FCC.
Currently, 25 countries use the NANP, including the U.S., Canada, all U.S. territories, and several Caribbean countries. There are 404 NPAs under the NANP, with the U.S. having the majority with 335, followed by Canada with 42. The Dominican Republic has three NPAs, while Jamaica and Puerto Rico each have two NPAs. Each of the other countries using the NANP has one NPA. Service NPAs are sorted into geographical and non-geographical divisions.
What are Special Numbers in the North American Numbering Plan?
Special numbers in the North American Numbering Plan are numbers that have been reserved for special purposes and cannot be assigned to service territories. These numbers are:
0 - Operator assistance
00 - Long-distance operator assistance (formerly 2-1-1)
011 - International access code using direct dial (for all destinations outside the NANP)
01 - International access code using operator assistance (for all destinations outside the NANP).
101-xxxx - Used to select an alternative long-distance carrier
211 - Local community information or social services (in some cities)
311 - City government or non-emergency police matters
411 - Local telephone directory service (Some telephone companies provide national directory assistance)
511 - Traffic, road, and tourist information
611 - Telephone line repair service (formerly 4104), wireless operator customer service (formerly 811)
711 - Relay service for customers with hearing or speech disabilities
811 - Dig safe pipe/cable location in the United States, non-urgent telehealth/tele-triage services in Canada (formerly telephone company business office)
911 - Emergency telephone number – fire department, medical emergency, police
950-xxxx - Feature group code for access to a carrier from a non-subscriber location. The feature requires the customer to dial a 950-xxxx number and enter a calling card number and destination telephone number. It was originally used for locations where 101-xxxx dialing was not possible
958-xxxx (local); 959-xxxx (long-distance) - Plant test numbers, such as automatic number announcement circuits. It was once common to reserve entire unused exchange prefixes or N11 numbers (4101 was the ringback number on many step-by-step switches), but these have largely moved to individual unpublished numbers within the standard 958-xxxx (local) or 959-xxxx (long-distance) plant test exchanges as numbers become scarce
1-NPA-555-1212 - Non-local directory information (Canada and United States)