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Useful Notes / North American Numbering Plan

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A bit about making phone calls in the United States, Canada, and select other areas.


The fact that it's called the North American Numbering Plan should clue you in that it's not just a US thing. Or even a US/Canadian thing. The NANP actually covers 25 distinct regions in 20 different countries. Most of them are in North America, including the Caribbean. However, many countries in the northern part of the Americas, most notably Mexico, are not part of the NANP, while some regions far removed from North America are part of it (namely, US territories in the Pacific).


NANP territories are:


A brief history

From the invention of the telephone in 1876 through the first part of the 20th century, the Bell System (which operated in both the US and Canada) grew by incorporating local or regional telephone systems. Each system established its own numbering plan, with calls within specific local areas handled by a central office (an "exchange") and subscribers receiving a number within their exchange. While all exchanges had numbers, they were identified by letters, which in turn designated certain memorable names. (This explains why North American phones, even today, have letters mapped to their numbers.)

Works from this era will frequently reference this system. For example, the Hotel Pennsylvania in Manhattan, a major venue for big band music, inspired the song "Pennsylvania 6-5000", famously performed and recorded by Glenn Miller and his band.note  In that era, the number would have been written either as the title or in the short form "PE 6-5000" (the first two letters, not the postal abbreviation). This was the real phone number for the hotel's front desk, and remained so until the hotel closed in 2020. Nowadays, the number is written as 212-736-5000.

This system was far from uniform. Most central offices used two letters and five numbers, but a fair number used three letters and four numbers, and some small exchanges had numbers as short as five digits (two letters, three numbers). On top of that, Montreal and Toronto, among other areas, had a mixture of six- and seven-digit numbers. Needless to say, this mishmash of incompatible local systems proved to be a major obstacle to creating a continent-wide system for long-distance communication. With that in mind, the Bell System sought to unify all of the varied numbering plans throughout the US and Canada into a single plan.

In 1947, the Bell System, in cooperation with independent local phone companies, published a new numbering plan. Most of North America was divided into 86 zones known as numbering plan areas (NPAs). Each was assigned a three-digit code, formally known as an NPA code but more commonly as an area code. These codes were first used in operator toll dialing, in which a caller contacted an operator to place a long-distance call—as depicted in the Chuck Berry song "Memphis, Tennessee". Direct distance dialing (i.e., customer-dialed long-distance) would start in 1951. However, only 12 cities, all in the US, had the switching equipment needed to allow DDD. Over the next decade-plus, as all of the US and Canada standardized on seven-digit numbers and other areas upgraded their systems to allow DDD, it would be rolled out—though some remote areas didn't get DDD until the 1970s, and operator-assisted dialing lingered on for a few more years after that. Indeed, the 1972 Jim Croce song "Operator (That's Not the Way It Feels)" depicts a man talking with an operator to try to reach his former girlfriend.

In 1958, the Bell System introduced all-number calling, eliminating the former use of letters to identify exchanges. This was done in large part because in many heavily populated states/provinces, it became necessary to use digit combinations that could not be expressed by memorable names.

Also in 1958, Bermuda and the British West Indies were added to the plan at the request of the UK government, largely because their telecom systems had historically been administered through Canada. The Dominican Republic and the US territories in the Caribbean also joined, but Cuba, Haiti, Central America, and the French and Dutch Caribbean chose not to. Saint Pierre and Miquelon, a French territory off the Canadian coast, also chose not to join. Attempts were made to integrate Mexico into the NANP, and three area codes had been assigned to the country, but it chose to adopt an international format, and those codes were reclaimed in 1991 and eventually assigned to other North American areas. Incidentally, the actual name of "North American Numbering Plan" didn't appear in print until 1975.

The US territories in the Pacific, apart from the state of Hawaii, were not part of the NANP for decades. They used an international format, with their own country codes. In the years surrounding the turn of the millennium, those territories joined the NANP, with their former country codes becoming NANP area codes. The most recent addition to the NANP is Sint Maarten, a Dutch possession in the Caribbean that joined in 2011.

When the Bell System was broken up in the 1980s, the US Federal Communications Commission took over oversight of the NANP, with day-to-day administration in the hands of the North American Numbering Plan Administrator. The FCC periodically solicits private sector contracts for the NANPA role; it's currently in the hands of a company called Somos. Each participating country has full control of its numbering resources, but all cooperate with NANPA.

The telephone system

All phone numbers in the NANP consist of 10 digits, typically written in the format xxx-xxx-xxxx.note  The first three are the area code, followed by a seven-digit subscriber number, in turn split into a three-digit central office code (also known as an "exchange") and a separate four-digit number. The numbers have certain limitations:

  • Area codes:
    • The first digit of the area code cannot be 0 or 1. This has applied throughout the NANP's history.
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    • The second digit can be any number. Originally, this digit had to be 0 or 1; this restriction wasn't removed until 1995.
    • The third digit can be any number. However...
      • The eight codes of the form N11, where N is 2–9, are reserved as service codes.
      • Additionally, the code 988 has been reserved in the US as a national number for suicide prevention helplines. Canada is also reserving this code for the same purpose.
      • NANPA also does not issue "easily remembered codes", specifically those which repeat a single digit three times. (Except 888, reserved for toll-free calling; see below.) When NANPA was preparing to split Nevada's original 702 area code, with the Las Vegas area retaining 702, the state wanted the new code for the rest of the state to be 777 (as in "lucky 7s"). The state was turned down; when the split was activated in 1998, the new code ended up as 775.
  • Exchanges (central office codes):
    • Initially, 0 and 1 could not be used in either of the first two digits of exchanges. "0" was used for operator assistance, while "1" was automatically ignored by early switching equipment. Also, the old system of using memorable names for exchanges was incompatible with the use of 0 or 1, because letters were (and still are) not assigned to those digits. These numbers are still prohibited in the first digit, but since the 1970s they have been allowed for the second digit.
    • Though as with area codes, the N11 codes can't be used for exchanges.
    • As for 988, since it's been used as a central office code for decades, implementing it as a national number meant that the areas that used it as an exchange and still allowed 7-digit dialing had to either (1) retire the exchange and issue new numbers to subscribers that already had a 988-xxxx numbernote  or (2) require 10-digit dialing.

In recent decades, NANP area codes have been adopted as nicknames for certain metropolitan areas. The Trope Codifier for this is Toronto, where "The 416" refers to the city proper of Toronto (though it's more recently been replaced by "The Six"; see that city's page for the explanation) and "The 905" to its suburbs (still in wide use). Other examples include:
  • The 757: The Hampton Roads region of Virginia (Norfolk, Virginia Beach, Chesapeake, Hampton, Newport News, etc.). This is especially notable as it's the most widely used nickname for the area as a whole.
  • The 216: Cleveland and vicinity, though "The Land" is more common these days
  • The 404: Atlanta inside "The Perimeter" (Interstate 285, which encircles the city), though "The ATL" is much more common now
  • The 804: Richmond, Virginia and its surrounding area, though "RVA" is more common now
  • The 450: Commonly used by Montreal residents to refer to Laval and the off-island suburbs, which split off from 514 in 1998 note 

In all cases, these refer to the areas' original area codes; most (though not all) have since become subject to overlay plans (explained below).

Speaking of 10-digit dialing: Between 1947 and 1992, people needed only to use the local telephone number to make calls within their exchange, or within their area code, a system that became known as "7-digit dialing" once that became the standard number length. (At least for landlines; cell phones have always required full 10-digit dialing everywhere.) That said, some switching systems required dialing "1" before the number to indicate a toll call. Calls to numbers in different area codes, even if they were within a caller's local calling area, required 10 digits (again, some switching systems also required "1" first). During that period, whenever the demand for numbers within an area code neared capacity, that area was split into a number of suitable parts (usually two), with one area keeping the old code and the other(s) receiving new codes. However, beginning in 1992, overlay plans, in which a given geographic area can have more than one area code, were adopted as another means to deal with number exhaustion. Canada went all-in on overlay plans early because of its inefficient number allocation system (see The Other Wiki for more details). The US was slower to adopt this, but following New Mexico's area code split in 2007, every new area code in the US has been part of an overlay plan.

Do keep in mind that calls between countries in the NANP are billed at higher rates than domestic calls. This includes calls between the US and its territories. Calls between the US and Canada are billed as international calls, although at a lower rate than calls to most other third countries (or, indeed, those between the US and its territories). Historically, long-distance calls within the US or Canada were billed on a distance-based model, with calls from the contiguous US to Alaska or Hawaii often having their own special (higher) charges. Also, because of taxation issues within the US, landline calls within a state can cost more than a call across the continent but still within the US. This is mostly a Dead Horse Trope for purely domestic calls; most US landline plans and almost all US cell phone plans now include unlimited domestic long distance within the 50 states (and Washington, DC), and a relatively small monthly charge will add unlimited calling to Canada and the non-NANP country of Mexico. Analogous plans are commonplace in Canada (unlimited calling within Canada, with unlimited calling to the US proper for an added monthly charge).

The international code is 011 (country number) for outgoing calls.

To call into any NANP area, use its international code of 1.

In the United States and Canada, the number 555 is generally available as a fictional exchange number. The United Kingdom also has a set of numbers available for this purpose.

Unlike many countries, mobile phones in the NANP's most populated territories of the US and Canada are not assigned their own set of numbers.note Added note  They receive numbers within the same geographic calling areas as landlines. This setup has both advantages and disadvantages:

  • A huge advantage (in the US and Canada only) is that as long as you stay within the same area code, you can freely swap your phone number between a landline and a cell phone, in either direction.
  • A significant disadvantage is that should a disaster knock out phone service in the area where your cell number is assigned, you may end up being able to make calls but not receive them—even if you're hundreds or even thousands of miles away from the disaster. That's because incoming calls need to be routed through equipment in the damaged area. This first received significant publicity in the aftermath of Hurricane Katrina.
  • In most countries, especially where cell phones are assigned numbers in separate blocks from landlines, calls to mobile phones are charged at higher rates than those to landlines (a "caller pays" model). Because mobile numbers in the NANP are assigned within geographic area codes, this was impossible, at least in the US and Canada. Instead, mobile phones in the US and Canada are charged for airtime in both directions (a "subscriber pays" model). This system was arguably fairer to the public as a whole, as the subscriber is paying for the perceived convenience of accessibility on the road. Before the mid-2000s (decade), people tended not to give out their cell numbers indiscriminately for this very reason. However, virtually all mobile service providers now offer unlimited calling plans at competitive rates, with no extra charge for domestic long distance. This also contributes to a phenomenon in which people will keep their cell phone numbers for years after they move from the area where they originally got them, as noted in this xkcd comic.note 

Toll-free calling historically used area code 800. With demand increasing for toll-free numbers, codes in the 8xx range have been rolled out; currently, 888, 877, 866, 855, 844, and 833 are used as well. The former use of letters to designate exchanges does, however, have a lasting legacy: many businesses pay to receive toll-free phone numbers that map to their names or a word that describes their business. To name just two examples, the Discover credit card uses 1-800-DISCOVERnote , and a certain national florist chain uses 1-800-FLOWERSnote . There's even a plumber in Louisville, Kentucky whose name conveniently maps to one such number, and his business uses that number.

The 900 Number (area code 900) is a pay calling line ("premium rate" in the UK), usually used for sex chat lines or competitions. The 976 exchange is the local version of the 900 number, as seen in the 1988 horror film 976-EVIL and its 1991 sequel.

Each N11 code has its own unique uses, at least in the US and Canada:

  • 211 – Community services and information
  • 311 – Non-emergency number for municipal government services
  • 411 – Directory assistance (supported by most, but not all carriers). Now usually a pay service, since numbers can now be easily accessed by other means (i.e. the Web).
  • 511 – Traffic information, or police non-emergency services (not implemented on a national basis)
  • 611 – Telephone company customer service
  • 711 – TDD and relay services for the hearing-impaired
  • 811 – Underground public utility location (aka "call before you dig") in the US; non-emergency health and information services in Canada
  • 911 – Emergency number
    • Many mobile phones will automatically direct calls to certain other emergency numbers—specifically the 112 used by most of Europe and the 999 used in the UK—to 911.