From the American FactFinder website: this source provides access to data about the United States, Puerto Rico, the U.S. Virgin Islands, Guam, the Commonwealth of the Northern Mariana Islands, and American Samoa. The data in American FactFinder comes from several censuses and surveys.
From the Urban Institute’s website: the Urban Institute is the trusted source for unbiased, authoritative insights that inform consequential choices about the well-being of people and places in the United States.
From the National Historical Geographic Information System website: the NHGIS provides free online access to summary tables, time series tables, and geographic information system (GIS) files incorporating all available aggregate census information for the United States from 1790 through the present.
The Statistical Abstract of the United States, published since 1878, is the authoritative and comprehensive summary of statistics on the social, political, and economic organization of the United States.