Geographic Names Information System (GNIS) - GNIS contains information about over 2,000,000 geographic features shown on United States topographic maps. Each entry includes location information (State, county, and geographic coordinates) as well as the type of feature and the name of the topographic map that shows the feature. The database is produced by the U.S. Board of Geographic Names and the U.S. Geological Survey.
U.S. Gazetteer - The U.S. Gazetteer, produced by the Census Bureau, is a list of United States place names for populated places from the 1990 and 2000 Censuses. It includes information on places, counties, county subdivisions and zip code tabulation areas. The latitudes and longitudes given for places in these files are the center of population for that place, and may differ from the location given in the GNIS.