When properly used, information in city directories can lead you to many other sources. For instance, the year you first notice a person listed in a city directly may give you a clue as to when they arrived in this country. If an your ancestor's first entry in a city directory is 1908, you might look through passenger arrival indexes beginning around 1905. If you know they became a citizen, their 1908 listing might be a clue as to when you should begin looking for naturalization records. If your ancestor had grown children living at home for a number of years and they stopped appearing in the directory, this might tell you they had either passed away or left home to get married. So it would be prudent to check marriage or death indexes.
The address your ancestors lived at during federal census years is especially important. The United States census has been conducted every 10 years since 1790. Knowing the address your ancestor was living at in 1870, 1880, 1900, 1910 or 1920 can help you locate them in the census. If you've tried finding your ancestors in the census and failed, you may be able to locate them in the appropriate city directory using their street address. Learning to interpret the information in a city directory is also important. Older directories often reported persons living in boarding houses, especially when they moved to another city or changed jobs.
And newer directories contain even more information. The most recent R. L. Polk directories (www.citydirectory.com) include three sections. The first lists people by name, address and occupation. The second breaks the former list down alphabetically or numerically by street address and then the name and address of the resident. The third is a list of phone numbers sorted by exchange. Of course, you won't find any listing here if the person has an unlisted number. Above all, you'll find city directories helpful in locating relatives who have moved to other cities or just disappeared.
Many libraries throughout the country house older city directories for their region in their genealogy or history section, but they keep the current editions on the reference shelves.
The LDS Church has hundreds of these directories on microfilm and makes them available to their Family History Centers (FHC) which also have selected local directories on permanent loan. You can order almost any city directory from the Family History Library in Salt Lake City and view it at your local FHC. The most efficient method in searching these directories is to
search through the CD-ROM index of library holdings, then choose the city or cities in which you're interested.