Depending on what you're looking for, it may be a matter of identifying the current data and statistics available and then tracking back through time (see the various specific data and statistics research guides). You can also check the Social Work Resource Guide's page on Statistics or the Social Group Statistics Guide.
Provides tables of statistics at the national level and has essays describing what types of data has been collected over time in different topical areas.
An annual publication of statistics on all aspects of the U.S. beginning in 1878. We have the print copies on 3-West in the Census Alcove. Online copies are available from the Census website (at least when the federal government is open). The government stopped producing this in 2012, so the most current version is available as the ProQuest Statistical Abstract of the United States.
Link to another library research guide.