The National Archives and Records Administration is the official keeper of archived federal census records.
The Census Bureau has digitized the historical print volumes and made them available as PDFs.
AU's Library subscribes to the database Ancestry Library Edition which is a good source for information about individuals from historic Census data.
AU also subscribes to Social Explorer which contains data from the first Census in 1790 to the present day.
The Census Bureau has more information on the history of the census.
The National Historical Geographic Information System (NHGIS) provides free online access to GIS files (please send related questions to the Geospatial Research Lab) and summary statistics for U.S. censuses and other nationwide surveys from 1790 through the present.
Historical Statistics of the United States
