There was a grouping of residents by streets made in 1665 in New York. It was the Records of the Dutch Magistrates. The first directory listing was taken in the year 1752 in Baltimore. By the end of the 1700s many other cities had prepared their own directories, including Philadelphia, Charleston and New York. There were several publishers, but one most noted which continues as a publisher today, is R.L. Polk Company of New York and Detroit.
Through the years the city directories became more detailed by including more information. Other directories also became popular, such as telephone directories, organization directories and professional directories. Unfortunately many of the repositories where you will locate city directories may have missing issues. Information was also collected one year and published the next, so keep in mind that by the time it was published, your ancestor may have died or moved.
If you live near a large library, check to see if they have any of the directories published by Gale Research Company of Detroit, Michigan. These would be Directories in Print; International Directories in Print and City and State Directories in Print. They are periodical publications. From these you can obtain information on what directories are currently in print and what might be available.
Check the Family History Library Catalog online at FamilySearch International, to see what is available for your state and county of interest in the area of directories. Some may be on microfilm and available through a Family History Center.
To locate libraries with web pages, start looking at LibWeb-Library WWW Servers, http://lists.webjunction.org/libweb/. You can check by state as to which public, academic and other libraries have web page and from there check as to any listings they have of city directories. Also Google the name of a town or city where you believe you ancestor lived PLUS library PLUS city directory. You may have to refine your search to gain the results you need. Once a library is located, inquire about having photocopies made of specific pages from city directories that may list your ancestor.
An extensive collection of city directories on microfilm can be found in the Library of Congress, http://www.loc.gov/rr/microform/uscity/. They can be used in their Microform Reading Room, but using their web page lists as a guide, you may be able to find these city directories elsewhere. They have film for over 1,200 cities, towns and counties, for the time frame of approximately 1861 through 1960.
Another large collection of city directories is located in the American Antiquarian Society in Worcester, Massachusetts. Most of their nearly 7,000 directories were published before 1877. To learn more about the collection, check out their web page, http://www.americanantiquarian.org/directories.htm.
City Directories for circa 1930 are available at the National Archives. To check out what is available, go to http://www.archives.gov/genealogy/census/1930/city-directories.html. On a subscription basis Ancestry.com, and Fold3.com (formerly Footnote.com), both have numerous city directories available.
One of the best ways to find locations of city directories is to use the web page, City Directories of the United States of America. There are also some digital collections of city directories online. An example would be the Indianapolis City Directory Collection at the Digital Collections of IUPUI University Library, http://indiamond6.ulib.iupui.edu/ICD/. This consists of 14 Indianapolis city directories for 1858-1980.
Miriam Robbins Midkiff has a growing website listing Online City, County and Rural Directories that are available on Internet. Not all states have a showing, but a number that do make it worth checking at, http://sites.google.com/site/onlinedirectorysite/.
Genealogists should use city directories on a continuous basis. It should be on your check list of items to check. One simple entry can lead to other sources. A missing person may signal a death or a move. Perhaps the next year, you'll find the answer when a widow shows up in the same household.