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.
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.