Telephone exchanges - A Historical Site

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Los Angeles data for 1930 have been found and used to update that page.

Because some of the directories which were microfilmed for the collection in the Library of Congress are defective, I am looking for some missing information. If you are a collector of old telephone directories and can help with the information I need, or you know a collector of old directories who might be willing and able to help with the information, see the request for information below.

Recently some people have been routed to this site by search engines even though they were looking for information on cities that are not yet dealt with on the site. (For a list of the areas currently covered by this site, click here.) I apologize if you are looking for data we have not put up yet. In the meantime, please look for information on this database.

Today, telephone numbers in the United States are uniformly ten digits, to facilitate direct dialing from anywhere in the country. The first three digits, forming the area code, do not always have to be dialed from all locations when they are the same as the calling number’s code, but more and more it is necessary to dial 10 (or 11, with a 1 preceding) digits for every telephone number.

This was not originally the case. Telephone numbers had anywhere from 3 to 7 digits (I don’t believe there were any places with fewer than 3) depending on the size of the city, and calls outside your local area had to be placed with an operator even after most telephones had dials and local calls could be dialed. And in those days, the telephone companies did not believe people could memorize strings of more than four or five numbers, so in the cities with longer numbers, the first few were converted to an exchange name, of which only the first few letters were dialed. Telephone dials had sets of letters over the number, like this (in the United States; there were other arrangements in other countries):

ABC over 2

DEF over 3

GHI over 4

JKL over 5

MNO over 6

PRS over 7

TUV over 8

WXY over 9

and sometimes

Z over 0

though the Z was never, to my knowledge, actually used in an exchange name. Note that 1 had no letters, and the letter Q was not used. This arrangement was invented by an Amertcan Telephone & Telegraph Co. employee named W. G. Blauvelt, and a patent was even issued in 1922 for it, though the first use of it was in fact around 1920. The patent would explain why some other arrangements were used by independent companies for years afterward, though after the expiration of that patent it became a North American standard.

The origin of those exchange names is rooted in history. Telephone exchanges were originally manual. You picked up the phone, an operator on the other end of the line asked, “Number, please?” and you told her (the telephone companies very early standardized on female operators) the number, which she used to locate a jack on the switchboard. She’d know your number by an indication on that same board, so she could connect a line from one jack to another, and you’d be connected to the person you asked for.

After a while, they needed to have multiple switchboards in a city of any size. Each one was a separate exchange, and each got a name. You’d tell the operator the exchange name as well as the number, and the switchboards were set up so that connections could be made between telephones on different switchboards. (In the early days, there was no rule as to whether you gave the number first or the exchange name first; I remember a drugstore near my home when I was growing up that had in the window a book into which they’d pasted the prescriptions they’d received to fill many years ago, and the pages they showed were from the era I’m describing. The doctors’ phone numbers could be something like “1234 Marble” just as easily as “Marble 1234.” And I have seen microfilms of old directories with both arrangements; in New York City, for example, the directories issued about 1910 showed the number first and the exchange afterward, while a few years later this arrangement was reversed.)

When dial exchanges began, the system was set up so that you would first dial a prefix (one to three digits, depending on the size of the city) which connected you to the appropriate exchange, and then dial four (some large exchanges permitted five) digits to get you to the appropriate destination telephone. (I do not know how, in those pre-computer days, those large exchanges with both four- and five-digit numbers managed to cope with the fact that after four digits, the number might be complete or it might not.) If the destination exchange was still manual, which was possible since not all exchanges in a single city were converted at one time, the operator at that end got a display of the digits you dialed, which she used to complete the connection.

The biggest cities (New York, Chicago, Philadelphia, and Boston) had 7-digit telephone numbers. (Yes, Boston was one of the big four. It was considered a big city then!) Three were used for the exchange, so a number which might be dialed 244-5678 would be called (in New York) CHIckering 5678. Capital letters, as shown here, were used to show the particular letters you dialed. But it soon became clear that too many combinations could not be worked into names, and as early as December 1930 in New York, and in the late 1940s in the other three cities, it was decided to keep only the first two letters and use the third digit in numeric form. So CHIckering 5678 became CHickering 4-5678. On this site, both sets of New York exchanges will be given.

It might be noted that when New York changed, the exchanges were mostly changed in a way that left the numbers dialed the same, as in the example of CHIckering becoming CHickering 4, while in Philadelphia, the changes were made in the opposite way, almost always changing the third digit (SAGamore becoming SAgamore 2, not SAgamore 4).

In the next tier of cities, 6-digit numbers were used, with two-letter exchange names. When the time came to unify telephone numbers in a 7-digit format, several different systems were used.

Most of the smaller cities that used 5-digit numbers, and all of the very small towns that used 3- or 4-digit numbers, used all-numeric numbers, but some of the 5-digit places did write the first digit as a letter and make a name out of it. Very occasionally, the dials in those cities had names over the digits, not the standard ABC, DEF, etc., and those names were used for exchanges. (A small telephone company that competed with Bell in Philadelphia, Keystone Telephone, used this last system, as did perhaps 2 or 3 other telephone companies.)

A partial list of cities and the number patterns they used is available on this site: alphabetical by city and grouped by pattern.

This site was begun with a concentration on the New York City metropolitan area, and it is still most detailed in its contents relating to that area. Gradually, other cities are being added. For a guide to the areas which have available information, click here. New York city data have been tabulated separately for the pre-1930 three-letter and post-1930 two-letter eras, and analogous divisions are intended for each city tabulated, though the year of adoption of the two-letter, five-digit pattern varied for each city and the division point in the data similarly varies.

To aid in navigating the list of exchange names, they will be ordered in two or three different ways in each section. For an explanation of the ways the charts are ordered, click here.

I would like to thank the following people for their assistance:

  1. Anthony J. Brancato for supplying some information (especially, but not restricted to, exchanges in Staten Island) about the city of New York
  2. Roe Chin for some information on Staten Island
  3. Frank M. Foster for some information on the patterns of standardization in Ohio cities
  4. Charles Long, a former employee of the Bell Telephone Company of Pennsylvania (who has provided a large amount of Philadelphia data)
  5. Alan J. Sachs, who has tracked down some data on microfilmed directories of the pre-dial era in New York City which the Library of Congress has, for some reason, lost; and who has also sent much data on San Francisco exchanges at the beginning of the late dial era

Because of missing pages in the original directories microfilmed for the collection that I have consulted in the Library of Congress, there is information I need to obtain. I am looking for anyone who might have access to any of these directories:
  1. Nearly all directories with dates in the 1920s (different pieces are missing in different directories; please contact me if you have any).
  2. The Brooklyn directory dated Summer 1932
  3. The Brooklyn directory dated Winter 1932-1933
  4. The Bronx directory dated Summer 1938
If you have access to any of these, and are willing and able to help me, please send me an e-mail message.

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Last modified March 30, 2016.

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