Marilyn didn't tell you about Area Codes

Ask Marilyn ® by Marilyn vos Savant is a column in Parade Magazine, published by PARADE, 711 Third Avenue, New York, NY 10017, USA. According to Parade, Marilyn vos Savant is listed in the "Guinness Book of World Records Hall of Fame" for "Highest IQ."

In her Parade Magazine column of June 21, 1998, Marilyn explained that when telephone area codes were first assigned, the objective was to minimize the dialing of wrong numbers.

The Rust Belt is King

I'm writing to suggest an amplification to your answer regarding area codes in the June 21 issue of Parade. Your answer as to why the New York area code (212) is different from Westchester (914) did explain why they were different. But you didn't say why New York was 212, and Los Angeles 213. There is a reason, and it's related to the work in Information Theory done by Claude Shannon for Bell Labs.

The reason is that, in the early days of rotary dial phones, numbers were encoded by "clicks" as the dial returned to its inital position. That is: "1" was one click, "2" was two clicks, all the way up to ten clicks for "0". Lower numbers took less time to dial. When a phone was off-hook for dialing, it tied up one circuit of the phone network. To minimize the total number of circuits needed to handle long distance traffic, it made sense to have the most commonly dialed numbers require the least amount of time. Thus the most populous areas got the area codes which required the shortest amount of time (subject to the other constraints you mentioned, such as area codes being different from exchanges). Here are some examples:

Area               Code   "Clicks" to dial

New York City      212     5
Los Angeles        213     6
Chicago            312     6
Detroit            313     7
Dallas             214     7
Pittsburgh         412     7

Note the population levels when long distance numbers were assigned! The Rust Belt was king!

And it wouldn't be America if we didn't stick it to the poor folks in rural, low population areas:

Area               Code   "Clicks" to dial

Alaska             907     26
Hawaii             808     26
Eastern Washington 509     24
South Carolina     803     21
Montana            406     20
Wyoming            307     20
Idaho              208     20
Vermont            802     20

Nowadays, with Touch-Tone dialing, the numbers are encoded by tones that take the same amount of time regardless of the number. So the considerations mentioned above aren't important anymore.

But, in the days when all this started, there was a reason!

Keep up the great column

Thanks also to Charlie Kluepfel <ChasKlu@aol.com> who wrote with similar information.