Some family researchers believe it is necessary to find an old map to locate an old town. An old map will not necessarily show all towns in existence when the map was printed because small towns might have been omitted.
A useful tool for locating towns is a gazetteer, which is a geographical dictionary that lists place names (for example, those of states, territories, counties, cities, towns, and townships) alphabetically for a geographical region. The type of information given in various gazetteers differs, but usually the state and county (and sometimes township) [for example, in U.S. gazetteers] are listed. This information will help to locate a place name on a map and to determine the town or county in which the major records (for example, vital, land, probate) are located.
Taken from Schiffman, Carol Mehr, "Geographic Tools: Maps, Atlases, and Gazetteers." In Printed Sources: A Guide to Published Genealogical Records, ed. Kory L. Meyerink (Salt Lake City: Ancestry, 1998).