Another freebie from USGS is a catalog of published maps for each state, which gives map item numbers, prices of the USGS maps, plus an order form for obtaining them through the mail. The place names are arranged by state, showing the locality, latitude, longitude and other details. This is a great tool for finding places that may have been named for your family or obscure and tiny places. Historical atlases show the growth and development of the nation and the states, including boundaries, migration routes, settlement patterns, military campaigns, and Native American reservations. Academic libraries often have extensive collections of maps, atlases and gazetteers for the U.S. and other countries.
Many travel agencies offer excellent atlases of European countries at reasonable prices.
Discovering your ancestors' places of residence is critical to your research.