It turns out that you can get census data for censuses from 1790 to 1960. Want to know the population in 1790? Or maybe the slaveholding population? Or maybe the population of slaveholders who are themselves black? Or of Jews? By state? And by county? Or maybe literacy rates in various states in 1900? Or the number of people born in China, or in Russia? Just go to the United States Historical Census Data Browser.

The questions varied from census to census, so information that's available for one decade may not be available for others.