The original area codes (with 1 or 0 in the middle digit) were assigned based on population/importance of the city. Thus New York got the one with the fewest clicks: 212. LA and Chicago had 213 and 312 for 6 clicks each.
whirrrr - click - whirrrrrrrr - click - click - click - click - click...
Which is also why the original exchanges did not use the “0” or “1” as the middle digit. I also remember the “names” that were given to the local exchanges: my mom & dad’s number was 251-6334, which was pasted on the rotary dial as “CL1-6334,” which was the “Clifford” exchange. Bake’s 357 exchange was “Melrose.”