National Oceanic and Atmospheric Administration (NOAA) - Basemaps, ocean, coastal and atmospheric data, fishery, and weather data.
U.S. District Court Boundary Shapefiles (1900-2000) - Boundaries for each year provided for use in ArcGIS
Atlas of Historical County Boundaries
Provided by the William M. Scholl Center for American History and Culture at The Newberry Library,the atlas provides data about the creation and all subsequent changes (dated to the day) in the size, shape, and location of every county in the fifty United States and the District of Columbia.
US Census Data is available at American Factfinder 2.
TIGER shapefiles for displaying US Census Data are available from 1992 to 2013.
TIGER (Topographically Integrated Geographic Encoding and Reference database) has been around for 25 years! Happy Birthday TIGER! Take a look at the history and celebration!
Environmental Protection Agency - Data for superfund sites, brownfields, air quality reports, etc.
US Department of Agriculture - Data, Maps & Analysis on climate, watershed, soils, etc.
US Forest Service - Click here to select and find GIS data by region.
Bureau of Ocean Energy Management collects data on all facets of our offshore Oil and Gas Energy Programs and makes that information available in various formats. Visit BOEM Statistics and Facts.