IPUMS Census Microdata
Hosted by the University of Minnesota. The Integrated Public Use Microdata Series (IPUMS-USA) consists of more than fifty high-precision samples of the American population drawn from fifteen federal censuses and from the American Community Surveys of 2000-2011. Census data from 1850 to 2000, and ACS data from 2000 to 2011. This site also has data from the US Current Population Survey, and IPUMS-International with International data.