Abbreviation for the Geographic Names Information System. This free online database can help US genealogists locate obscure place-names, such as creeks, and small towns.
"The Geographic Names Information System (GNIS), developed by the USGS in cooperation with the U.S. Board on Geographic Names (BGN), contains information for almost 2 million physical and cultural geographic features in the United States and its territories. 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 is our Nation's official repository of domestic geographic names information.
"The GNIS also contains information on geographic names in Antarctica which are approved by the BGN for use by the Federal Government.
Source: Geographic Names Information System.