The U.S. Board on Geographic Names (BGN) maintains the Geographic Names Information System (GNIS), which contains information about almost 2 million physical and cultural geographic features in the United States. The Federally recognized name of each feature described in the data base is identified, and references are made to a feature's location by State, county, and geographic coordinates. The GNIS data includes physical features such as caves, forests and springs as well as cultural features such as churches, cemetaries and small populated places (see GNIS feature definitions). FAQ's answer many questions about place names in the US.
The GNIS is the official repository of U.S. domestic geographic names information. Information about foreign geographic feature names can be obtained from the GEOnet Names Server, developed and maintained by the National Geospatial-Intelligence Agency.
The Antarctica Geographic Names Data Base contains geographic names in Antarctica which are approved by the U.S. Board on Geographic Names for use by the Federal Government.
The GNIS United States and Territories Data Base Query Form provides online search of the GNIS Database. Results may be saved as a delimited file containing lat/long coordinates and then imported into GIS software. For example, with ArcMap, use the "Add XY Data" tool to import the table to a feature class.