Chicago telephone exchanges

The history of the telephone exchange names in Chicago, as in most significant United States cities, can be divided into three periods:

  1. The pre-dial period, when all telephone calls were completed by manual action by operators, and there were no constraints on exchange names other than that there was no likelihood of confusion when a customer gave the name to the operator,
  2. The early dial period, in which the Chicago telephone numbers were set up to accommodate dialing the first three letters of an exchange name followed by a four-digit number designating the individual line, though in fact not all exchanges provided for dialing by the phones in those exchanges, and
  3. The late dial period, whose beginning in Chicago was on September 18, 1948, in which, instead of the first three letters of an exchange name alone, one dialed the first two letters and an "office number" (This was the terminology used in an early New York City directory, though it was not common terminology in this period), again followed by four digits designating the individual line.

At this time, no information has been researched on the pre-dial period in Chicago. This material will be added as I find it out.

Main Chicago page
Chronological periods of the Chicago data:
Pre-dial period Early dial period Late dial period

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Last modified September 16, 2015.

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