In the sea of resources on the Web, a great deal of geographic information system (GIS) data is available free for download. The catch is you just have to know how and where to find it.
While general government agency Web sites like the U.S. Geological Survey (www.usgs.gov) and the U.S. Census Bureau (www.census.gov/geo/www/maps) contain plenty of GIS data ready for download, much of the data available on the Web is so widely scattered and hidden so deep within government agency holdings that it is difficult to know where to begin.
To help remedy this problem, the federal government has developed www.geodata.gov. As part of the Geospatial One-Stop initiative, this site is intended to serve as a portal for access to federal, state and local GIS data.
The intent of the portal is to