The area codes originally referred to geographical locations, as discussed above. The exchange originally referred to a local region. I remember when I could tell from the number in the exchange the approximate geographical location within a town. For example:
@tedibear, I know what you’re talking about. In the town where I grew up, our phone number, through the 1950’s, was something like Mytown 1234 (where “Mytown” is the town name). In order to place a local call, we would simply dial the four numbers (indicated by the x’s). However, to place a call to many of the neighboring towns, we had to place the call through an operator, with toll charges. Somewhere around 1960 (maybe a year or two earlier) the town name was dropped and an exchange name was used. The first two letters of the exchange name were intended to be a mnemonic for the first two numbers of the exchange. For example, the famous BUtterfield 8 exchange of movie fame would be dialed 288, with the last four digits of the number. This would allow numbers in a certain region to call using the seven digit number. Shortly afterward, the “North American Numbering Plan”: standardized Area Codes, giving each subscriber a unique 10-digit number. This plan, with a updates for number availability, is what is used today to assign numbers.