telephone numbers

In the telephone’s earliest days, there were no telephone numbers. A caller asked the operator for another subscriber by name, and prompt call routing depended on the operator's remembering who was where on the switchboard. (Perhaps verbal dialing will be a convenient option once again when computers can interpret common speech.)

In 1879 a measles epidemic led Moses Parker, a physician in Lowell, Massachusetts, to suggest that each subscriber be given a number, so that the system would not be paralyzed if all four of the town’s operators fell ill.

As the number of subscribers grew it was necessary for a city to have more than one exchange. Callers then asked for the exchange plus the number. In smaller towns a 3 or 4 digit number might still be sufficient.

photograph of a rotatry dial phone In 1921 dialing began to replace operators. The original dial was a spring-loaded disc with ten fingerholes numbered from 1 to 0. By placing a finger in one of the holes, the disc could be rotated to a stop. When the finger was removed, the dial returned to its original position, making a pulse each time a number was passed.

In order to transmit the names of exchanges, each of the eight holes from 2 to 9 also represented 3 letters of the alphabet. (In 1917 a two-letter code had been established for the names of the exchanges.) Q was omitted and eventually Z as well. The first group, “ABC” was put with the numeral 2 instead of 1 because a single pulse could be accidentally created by lifting the receiver. Thus, no numbers could begin with 1.

Seven-digit numbers–adding an extra digit between the 2-letter prefix for the exchange and the 4-digit number–originated in New York City in the early 1930s and became standard after World War II. In 1961, exchange name dialing began to be phased out in favor of an all-number system, a change completed in 1978.

Area codes

table of United States, Canada and Caribbean area codes

Direct dialing of long distance calls, which began in 1951 in the United States and in 1958 in Canada, required an additional string of numbers, which were named “area codes.” The first digit could only be 2 through 9. The second digit was 0 or 1, and the third 0 through 9, except that all numbers with a 1 in both the second and third positions were reserved for special uses (e.g. “411” for information, “911” for emergencies), as were numbers with a 0 in both those positions (e.g., “800” for toll-free calls, “900”). This left 144 possible area codes, which seemed ample until the fax machine and cellular phone arrived.

To create new codes, it was decided to allow the second position to be occupied by any numbers from 2 through 9, in addition to the 0 and 1 already used, creating 640 possible area codes.

In the United States, international direct distance dialing began in March 1970.