For researchers needing the detailed decennial U.S. Census data tables and American Community Survey sampled data tables, the National Historical Geographic Information System (NHGIS) https://www.nhgis.org/ provides census and American Community Survey data. Census information spans from 1790 to recent American Community Surveys.
Don’t let the GIS part scare you. The tables with the data are downloaded separately from the GIS shapefiles.
Registration is required. The interface will be familiar to frequent users of U.S. Census data.