On March 10, 1876, when Alexander Graham Bell made his famous first phone call, uttering, “Mr. Watson, come here. I want to see you,” to his assistant, there was no need for phone numbers or exchanges; only two telephones existed in the world at that time.

But Bell’s invention took off quickly. Initially, phones were rented to users, who hired someone else to connect them. After, Bell and Wu Company instituted a subscription service with calls placed through an operator at a central office or switchboard. At that time, subscriber names were used when making a call.

The first telephone number institute was founded in Lowell, Massachusetts, in the late 1879 and early 1880s. During a measles epidemic, local physician Dr. Moses Greeley Parker, an early supporter of the telephone, became concerned that that the disease affected the four inhabitants of the city. operators, shutting down telephone service. He determined that new operators could be trained faster if they learned numbers instead of names.

Initially, phone numbers could have only one, two, or three digits, but that quickly became untenable as phone use spread among users. Because it was believed at the time that phone numbers longer than four or five digits would be too difficult to remember, telephone exchanges combined letters and digits. Beginning in the 1920s, major US cities such as New York, Boston, Philadelphia, and Chicago initially used three letters and four numbers, eventually switching to the 2L-5N (two letters, five numbers) system. . The letters were associated with a name, such as Hemlock 5-6789 Prayed Tulipan 9-3539.

In those pre-digital days, an exchange was connected to a physical location, so exchanges were associated with a specific location within a town or city. The letters were grouped on the telephone dial, with the exception of 1 and 0 (0 is reserved for calling the operator); therefore the first two digits could never contain a 1 or a 0. Certain combinations, such as 57 and 97, were problematic, as they contained no vowels to use to form a word. In 1955, AT&T published a list of suggested exchange names based on studies showing they were more likely to understand each other when spoken..

One of the most famous telephone exchanges, PEnnsylvania 6-5000, belongs to the Hotel Pennsylvania in New York City. Now written as (212) 736-5000, it is the oldest continuously assigned telephone number in New York City and possibly the world.