Historic Census Materials:
Historical Census Publications electronic versions at the University of Michigan Library.
One stop shopping for Historical Census Reports 1790-2000. Includes links to Historical Census Browser (UVL), National Historical Geographic Information System (NHGIS), and the Historical Reports, Census of Population and Housing, US Bureau of the Census.
http://www.lib.umich.edu/govdocs/hiscenpub.html
Historical Reports, Census of Population and Housing, US Bureau of the
Census. PDF files of selected decennial publications covering 1790-2000.
http://www.census.gov/prod/www/abs/decennial/index.htm
Historical Census Browser ,University of Virginia Library, Digital Research and Instructional Services, Provides selected population statistics for states and counties from 1790-1960. Goes down only to county level.
http://fisher.lib.virginia.edu/collections/stats/histcensus/
National Historical Geographic Information System (NHGIS) (University of Minnesota. Minnesota Population Center) http://www.nhgis.org/
Provides aggregate census data and GIS-compatible boundary files for the United States between 1790 and 2000. Including small area data excluded from the Historical Census Browser.
Historical data in various formats from the Bureau itself Census Bureau's Selected Historical Decennial Census Population and Housing Counts
http://www.census.gov/population/www/censusdata/hiscendata.html
A Census publication from 1990 that includes lots of historical data including some place- (i.e., cities and towns) level data to 1790 http://www.census.gov/prod/cen1990/cph2/cph-2-1-1.pdf
Social Explorer provides easy access to demographic information about the United States, from 1940 to 2000. To get started, select "Maps" or "Reports”, for free data.