In the early days of direct dialing, as 7-digit telephone numbers were adopted, Ma Bell decided people would never get used to remembering or dialing such a long string of numbers.
The solution was adopt exchange names for the first two digits; indeed, telephone exchanges were actual physical structures and they were generally referred to by that name. Even now, when the building (probably) houses an all-electronic digital switch instead of banks of electromechanical relays and crossbars, is not limited to a single pair of leading digits in the numbers it serves and may serve ten times as many subscribers, telephone company employees tend to call the locations the old prefix-names.
I knew a few -- Broad Ripple's exchange is CLifford and in WW II, Homeplace/Carmel numbers were VIctory, though I don't know if the exchange on 106th St. had been built at that time. I figured any master list(s) from the telephone companies were long gone.
"Long gone" is not so gone as you might think -- here's the 1955 list of Official Exchange names from AT&T! The Web's enabling of of information packrattery never ceases to amaze me.
UPDATE: Old Grouch points out the use of exchange names-as-numbers dates back at least to six-digit telephone numbers. See Comments