Happy 312 day! — how Chicago got the 312 area code

I was about to wish everyone a happy 312 day. I previously never made the connection of 3/12 being a Chicago day, but thanks to the Art Institute Lions Twitter account, I realized 312 is an unofficial Chicago holiday.

But then I realized today is not 3/12, it’s 3/13. 313 is a Detroit area code.

The Detroit Free Press wrote an article about how they originally assigned the digits in area codes, including why Chicago has 3, 1, and 2.

Interesting clips from the article:

In 1877, just a year after Alexander Graham Bell patented the telephone, the first telephone message coming into Detroit played music from a concert in Chicago.

The call was made using another model of a telephone, made by engineer Elisha Gray instead of Bell, but a public audience of about 150 people were nonetheless delighted to hear the muffled music coming through the telephone box. Additionally, the 284 miles between the two ends of the line was the farthest distance that a call had gone through at the time.

in 1879, Detroit became the first city to assign individual telephone numbers, decades ahead of many other big cities like New York and London.

In 1947, the North American Numbering Plan was established to suit the growing population of the U.S.

First, states with one area code received a “0” in the second digit of their three-digit code, while states with multiple area codes received a “1.”

Then, the first and third digits of each area code were selected based off of the state or region’s prominence. Because phones at the time used the old-fashioned rotary dial system, lower numbers like “1,” “2” and “3” required less finger movement to dial than higher numbers like “7,” “8” and “9,” so telephone companies reserved these simpler area codes for the most populated cities with the most telephone traffic.

Because New York City had the highest call volume at the time, the city received the shortest three-digit number to dial: “212.”

The next cities were Los Angeles with “213” and “310,” then Chicago with “312.” Then, finally Detroit, among the country’s most prominent cities, with “313.”

Chicago has low digits because of the rotary phone! Love it.

Rotary by Jeff Boyd via Creative Commons on Flickr

Enjoyed this blog post?

Join the creatives who receive thoughtful Spudart blog posts via the email newsletter

Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Inline Feedbacks
View all comments
Would love your thoughts, please comment.x