Somebody recently asked me about the origins of telephone numbers. I told them to search my blog, assuming I must have written about numbering some time over the years – but I hadn’t.

The original purpose of a telephone number was to identify a specific customer. When telephones first came into use, they could only be used to call people in the immediate area who could be connected by the local neighborhood operator. Callers identified who they wanted to talk to by name. The idea of using telephone numbers started in 1879 in Lowell, Massachusetts, when the town was suffering from a measles epidemic. Dr. Moses Greeley Parker suggested that the operators assign a number to each of the 200 subscribers so that substitute operators would be able to complete calls if the normal operators became ill. Dr. Parker was so impressed by the telephone’s potential that he began buying stock and became one of the early largest shareholders in the American Telephone Company and New England Telephone and Telegraph.

In the early days, telephone numbers were short, with just enough digits to have a number for every customer. Some rural telephone switchboards only needed one or two digits. When telephone wires were strung in larger towns and cities, the exchanges needed to have more digits. New York City was the first place to use the seven-digit dial code, which consisted of two letters and five digits. The most famous example is Murray Hill (MU) 5-9975, the number for the Ricardos’ on I Love Lucy. The show was so popular that New York Bell Telephone created the fictitious number just for the show. The phone company assigned the two-letter code to represent a neighborhood, with Murray Hill being the east side of midtown Manhattan. For youngsters who have never used an old dial phone, the letters corresponded to numbers, and the letters were printed on the phone dial pad. The MU in Murray Hill translates to 68.

In 1947, AT&T introduced the North American Numbering Plan that mandated 7-digit dialing across 25 regions in twenty countries that covered the U.S., Canada, and the Caribbean. This plan used the country code of ‘1+’, which is why you can still dial a Caribbean island today using only the leading 1+, while calls outside of North America require a different country code. It took until the early 1960s for the numbering plan to be implemented everywhere in North America.

The current 10-digit dialing scheme was first introduced in 1951 as a way to help automate long-distance calls. Area codes were assigned geographically, with major metropolitan areas getting the easiest codes to dial, like the 212 for New York City. For many years, calls could still be made within a region using 7-digit dialing, and the extra 3-digits for the area code were only required to make a long-distance call outside a region. The first place to mandate 10-digit calling for local calling was Atlanta, Georgia, which implemented 10-digit dialing ahead of the 1996 Olympics. This stopped visitors from other parts of the country from making local calls when they intended to dial somebody in their home state. The transition to mandatory 10-digit calling was implemented across the country over the next several decades, as adopted by State Regulatory Commissions. Full mandatory 10-digit dialing wasn’t implemented everywhere until 2021, when the FCC mandated the 988 Suicide & Crisis Hotline number.

Telephone numbers stopped representing specific neighborhoods when the Telecommunications Act of 1996 mandated local telephone competition and number portability, meaning that a customer could change carriers and keep the same number. In 1998, the FCC mandated number portability to the top 100 metropolitan areas. I remember asking for a new telephone number in the DC suburbs around that time and being offered a number from different towns as far away as Annapolis. If you moved outside the metropolitan area, you had to get a new number.

In 2003, the FCC ordered Wireless Local Number Portability, which fully decoupled the telephone number from a location. From that point forward, a person could keep their cellular number anywhere within the North American numbering plan.

Landline numbers became fully portable with the introduction of Voice over IP. VoIP providers like Skype and Vonage hit the market in 2003, and States and the FCC began allowing VoIP numbers to be used from anywhere.