IPUMS-USA 1850 to 2004 (Integrated Public Use Microdata Series from University of Minnesota).
Quick links to Census 2000 data
Historical Census Data for San Diego (1950-2000)
Census of Population and Housing, 1990 [United States] Series
Census of Population and Housing, 1980 [United States]
Census of Population and Housing, 1970 [United States]
Census of Population and Housing, 1970 [United States] Series at ICPSR
Census of Population and Housing, 1960 [United States] Series at ICPSR
Census of Population and Housing, 1790-1950 [United States] Series at ICPSR