This is one of a series of tables covering the 1920-1930 period, and if you
have not already read the information on the master page of
the set, you are advised to do so.
The telephone directory dated "November 17, 1920" was the first directory in which the subscriber listings were included in a form that implied the use of dial telephones. The basic list continued the three-section format that had been in use prior to 1920, with a section for Manhattan and the Bronx, one for Brooklyn and Queens, and one for Staten Island (under its then-official name, "Borough of Richmond"). The only substantial change was the way the numbers were listed in the directory listings. Where previously, a listing had been in the form "Blythebourne 27," it would now be given as "BLYthebourne-0027": the first three letters of the exchange name were capitalized, and if the numerical part were less than 1000, additional zeros were prefixed to build it up to four digits. (In the Staten Island section, listings were written as "Tottenville-0012," without capitalizing the first three letters of the exchange name, but with all the numbers expanded to four digits.) Note that at that time, a hyphen was put between the exchange name and the four-digit (or occasionally five-digit) number in the subscriber listings, but when numbers were referenced in advertisements or other places in the book, sometimes there was a hyphen and sometimes a space.
Certainly, not all the telephones in New York City (or even in the four major boroughs) were equipped with dials. In fact, exchanges were converted over a period on more than 20 years, extending well past the 1930 end of the period being discussed here; it was essentially completed in 1942, but one exchange remained manual nearly until 1960. However, if an exchange were manual itself, but could be dialed from other exchanges in New York City, it was necessary to give the listings the format that showed how to dial the number.
Although this period was very short, covering just ten years (The pre-dial period covered more than 30 years, and the late dial period at least as long as that, depending on exactly when it was considered to end; if the late dial period includes the use of all-number calling, it lasted over seven decades and is still going on, but my own preference is to consider it to have ended with the end of letter exchanges in the mid-1970s, which would make it about 45 years.) there were three distinctly-different directory types:
Two types of list of exchanges were presented in the telephone directories. There was a list of exchanges with their business office managers (designated on this website as a B list) as well as a listing of all the exchanges in the city and their zone, for purposes of cost determination (designated on this website as a Z list). (New York City was originally divided into to zones numbered from 1 to 10; in the May 1930 directories the number of zones was increased to 15.) In the chronology pages for the late dial period, six separate charts are provided. This is necessary because there are certain dates for which no directory had Z lists, which covered the entire city. It was not possible to deal conveniently with the comings and goings of exchange names on a city-wide basis when all that were available were borough B lists. However in this section of the site, covering the early dial period, this problem does not exist, since every directory had both a B list and a Z list. Consequently, the chart for this period is compiled only from the Z lists, and is city-wide. (The B lists, however, were consulted and if there are discrepancies, taken into account.)
It should, however, be noted that the capitalization of the first three letters in the exchange names was only in directory listings, advertisements, and other places where a specific number was given (such as the listings of police and fire emergency numbers). While a number would be given as, say, SPRing 3100, the exchange lists at the beginning of the directory, which is the source for these compliations, would show the exchange as simply "Spring" without the other capitals. But in all references on this site, the capital-letter convention for letters actually dialed is maintained.
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Last modified February 19, 2015.