Gazetteers provide the correct spelling of a location as well as the official combination of town, township and county. Use them to clear up problems when the same name occurs in more than one location. Postal Guides lists all towns with post office. They help when you can find no other directory or gazetteer for an area. Check Bullinger's Postal and Shipping Guide for the United States and Canada at your library and the U.S. Directory of Post Offices.
City directories are an underused source.
Genealogists tend to forget about them or are not aware that they exist for many locales since the early 19th Century. There are directories for cities, counties and states. Many contain the names of all heads of families in an area, their addresses and sometimes their occupations. Some directories were sold by subscriptions and only list the names of subscribers. If your ancestors did not subscribe their names will not appear, but don't assume they did not live there until you have consulted other sources.