The National Historical Geographic Information System (NHGIS) provides, free of charge, aggregate census data and GIS-compatible boundary files for the United States between 1790 and 2012.
Highlights of the NHGIS include:
- State and county aggregate data and boundary files (1790-2012)
- Census tract aggregate data and boundary files (1910-2012)
- Census data at all geographic summary levels, including census blocks (1970-2010)
- Boundary files for metropolitan statistical areas (1950-2012)
- Boundary files for all standard geographic summary levels (1990-2012)
- County Business Patterns data (1970-2003)
- SABINS aggregate data and boundary files for School Attendance Boundary Zones, covering each grade, K-12, for many school districts throughout the nation (2009-2010 academic year)
Additional background information is provided in the article: Fitch, C. A., and S. Ruggles. 2003. Building the National Historical Geographic Information System. Historical Methods 36(1), 41-51.