City directories are the ancestors of today's residential white pages and commercial yellow pages (in print and online). Some are available online, while many others are only available on microfilm. Some date back to the 1700s.
Researcher should be aware that although many directories are available there may not be an unbroken chronological series for your towns of interest. Sometimes a year or five years may be missing.
The directories may provide such details for your ancestors as the full names of husband and wife, children's names, occupation, employment and others at the same address. Often, maps were included. Since town plans changed as they grew, these original street names and locations may be very different from today's modern maps, and the old maps will help you pinpoint locations important to your family research.
To see how directories can help your quest, click here for an interesting analysis. The directories can help you compare family members from one year to the next, compare residences, business, given names (immigrants often changed both given and surnames) and other details.
Accessing data for the locations and the years your ancestors lived there may provide surprising details.
While many large collections are only available in person, other collections are beginning to appear online, such as those at Distant Cousin . Genealogist George C. Morgan's article on comparing telephone directories with city directories will be useful to learn more. click here.
The image below is a small section from the 1884 Toronto, Ontario, Canada directory:
The US Library of Congress (Washington, DC) holds directories for more than 700 American cities and towns on microfilm. It has a separate collection of microfilmed US business directories 1902-1935, in addition to a pre-1861 US directories.
There are also international directories available. For example, JewishGen offers the online searchable index of the 1929 Polish Business Directory, with data for more than 34,000 locations for trade, industry, handicraft and agriculture.