Free Geography Tools

The National Historical Geographic Information System (NHGIS; free registration required for access) offers historical census data from the first census (1790) to the most recent. The types and extent of the data depend on the census year, with more data typically available from more recent census years. Data can be accessed for the entire country, by state, county, census tract, or other divisions where available, and can be downloaded in a number of different spreadsheet and GIS-compatible formats. The site also has shapefiles for the states/territories, counties, and census tracts appropriate for each census year. Online mapping of, and access to, some of the data from 1940 on is available for free at the Social Explorer website; Social Explorer offers full access to much more data and online maps as a paid service.