Geographic information systems (gis)
The 1990 and 2000 decennial census boundary files available here are selected generalized extracts from the Census Bureau’s TIGER geographic database and are designed for use in a Geographic Information System (GIS) or similar mapping system. The cartographic boundary files on this site are available in ARC/INFO EXPORT (.e00) format, ArcView Shapefile (.shp) format, and ARC/INFO Ungenerate (ASCII) format. These are the boundary files without the demographic data in the attribute tables. Tabular data may be downloaded from American Factfinder (http://factfinder2.census.gov/) and used in conjunction with the boundary files.
The National Atlas data is now archived as 1997-2014 Edition of The National Atlas of the United States on the U.S. government’s www.data.gov website.
The USGS continues to make at least a subset of the National Atlas data available under its National Map Small Scale Collection.
The GIS DataDepot is a commercial data site that has numerous data holdings available for free download. Additional data may be downloaded via a “Premium” option or written to CD-ROM for a fee. No-fee registration is required to download even the free data. Coverage is worldwide but generally not very detailed (VMAP0). US coverage includes TIGER/Line files; soils data (STATSGO and SSURGO); DEMs; and transportation, utilities, hypsography,and vegetation data at 1M.
This government site provides free downloads for frequently used datasets of California, including basemaps, elevation, transportation, political boundaries, scanned USGS topographic maps and 2005 and 2009 aerial photography.