A reverse telephone directory is an accessible listing of residential, businesses and organization's phone numbers. The directory allows an individual to track a phone number and, if the number is listed, get information about the caller, such as the caller's name and address.
Most states, including the states of Illinois and Florida, operate telephone directories for listed numbers where a person can start a reverse directory search. The telephone search tools require the complete telephone number, including the area code and the local phone number. Most states also allow a general telephone search where the online system searches phone numbers of all businesses, employees and agencies. New York State also allows the public to make an individual phone record search on its public phone directory.
Using the reverse telephone directory, individuals can also identify the geographical location corresponding to the phone number's area code. This helps to know where the unknown caller is calling from.
Additionally, such directories provide a map pinpointing the exact location of the caller. Through it, these directories enable people to get the directions to the place using the name and telephone number of the phone owner.
Once a number is identified as a sales or promotional call or as a wrong number using the reverse phone directory, individuals can determine if they need to call back.
Further, the reverse phone directory helps to determine if the calls to an unknown number, as indicated on the bill, were genuinely made by an individual. This way, the person can identify any errors in the phone bill and pay only for the calls he made.
For people who may wish to look up phone numbers dating back from the 19th and 20th centuries, the Library of Congress Business Reference Service holds a substantial amount of historical reverse telephone and address directories. This reference service is useful for businesses researchers and genealogists who need to make a historical research. The telephone numbers and addresses are accessible in the inventory of crisscross and street address directories in The Library of Congress' local history and genealogy reading room.