Exchanges in the city of Baltimore, Md.

The history of the telephone exchange names in Baltimore, 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 Baltimore telephone numbers were set up to accommodate dialing the first two 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, in which, instead of the first two 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, I have no information about the Baltimore exchanges in the pre-dial period or the early dial period, and only limited information about the late dial period, mostly derived from one directory (and some of the listings in that directory are not clearly readable), so the data on this site are very limited and incomplete. To access this information click here.

It does appear, from examination of the exchange names that I have, that Baltimore, like Washington, D. C., adopted a policy, when the late dial period started, of selecting the office numbers such that they were equivalent to dialing the third letter of the exchange name.

Other regional tables:

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Last modified March 9, 2015.

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