The tables that this page leads to give the exchanges in use in Chicago after September 18, 1948, when the format of telephone numbers changed from three letters and four digits (three-letter exchange names) to two letters and five digits (two-letter-one-digit exchange names). For the exchanges prior to 1948, please see the section of this website devoted to pre-1948 Chicago exchanges.
At the point of conversion from the three-letter, four-digit system, Chicago probably had more distinct exchange names than any other American city. It was the largest American city retaining three-letter, four-digit telephone numbers after New York City switched to the eventually standard two-letter, five-digit numbers in 1930. So while New York was able to reduce the number of exchange names in the 1930s and 1940s as the use of office numerals becane a way of distinguishing exchanges with the same name, Chicago continued proliferating exchange names in that period.
|Alphabetic table of exchange names|
|Numeric table of exchange names|
|Alphabetic/Numeric table of exchange names|
|Main Chicago page|
|Chronological periods of the Chicago data:|
|Pre-dial period||Early dial period||Late dial period|
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Last modified February 19, 2015.