Similar to the city directory is a county directory for rural locations. This type of directory is typically published by a land abstractor or realty company. The detail about each resident may not identify whether the family owns or leases land, and it may not identify land owners who live in nearby towns.
A city directory usually lists only heads of household and people who are "gainfully employed." Thus, through the 1960s, you might expect a city directory to contain a large majority of men. The few women listed before the mid-20th Century may be piece workers at home or owners of small shops that cater to women's needs, such as dressmakers, milleners (hat makers), cooks, and proprietors of boarding houses. Some publications offer lists of residents, some list businesses by category, some list both residents and categories of businesses. Some publications include ancillary information, such as lists of organizations, schools, churches, hospitals, and professionals by group. Many publications include street maps and voting ward maps. Almost all city directories include paid business advertisements, which is the primary source of income for the publisher. Sales of the directories is a secondary source of income.
The date of publication marks the end of a period of data gathering. The published information may be as much as as two years old, and almost certain to be at least a few months old. The data was usually amassed from responses to in-person interviews for smaller towns or a mail survey. Because the data was self-reported, it is relatively accurate for name spelling, occupation, and address. The absence of an expected name may not mean that the person has moved, but just that a respondent may have missed the deadline or decided not to participate.
The worth of directories for a city increases by comparing the listings over several years. A person may be skipped in one year and reappear at the same address—or a new address—the next year. Several years' directories help record the financial growth of a family, in which the children become part of the workforce and gain listings separate from their parents.
The future of city directoriesPerhaps the city directory will become less important or harder to use as demographics change in the United States. When fewer women take the family name of a husband, when blended families present two or even three surnames, the tracing of a family can become much harder to follow.
Several online sources have made inroads to the function of a city directory, most notably the White Pages and Yellow Pages. However, these alternatives are dynamic, and—as far as I know—no historical database has yet been developed as an online resource that may supplant the published city directory.
Where to find city directoriesMany libraries hold a full series of the city directories published for local cities, and most local historical societies hold local city directories. Several large libraries also have acquired a large holding of city directories, in physical books, microfilms, digitized records, or a combination of these media. The Family History Library of the LDS Church holds many city directories in its microfilm collection, and you can arrange for renting and viewing the microfilms at a local Family History Library.
Several online genealogy services include a search of city directories that are logged in their storage (e.g., Ancestry, Family Search).
Further researchTopic: Are city directories available for European cities and cities in the Middle East, Asia, and Africa?
Rootsweb Guide to Tracing Family Trees
Genealogy Research Associates listing of online and physical resources, in collaborative development
Distant Cousin online archive of searchable city directories
Miriam J. Robbins online listing for historical alumni, business, city, county, farm, Masonic, rural, social, and other types of directories