The National Histiorical Geographic Information System (NHGIS) includes Decennial Census data from 1790-2010, as well as selected data from the American Community Survey, County Business Patterns, Census of Religons, Special city Censuses of Chicago & Detroit and more. All of this data is available for download along with the accompanying boundary files. This is the easiest way to import and use Census data in ArcGIS. Refer to the directions below for importing and joining tables with geographic boundaries. Free registration is required to download data.