The data collected by the decennial census have changed over the decades. In 1790, each household provided the name of head of family and the number of persons in each household in five categories.
By Census 2000, the short-form asked 7 questions of all residents, while the long-form added 26 population and 20 housing questions for about one in every six households.
In 2005, the American Community Survey (ACS) replaced the long-form, which allowed the 2010 Census to ask just 10 questions about each person. The results from the 2010 Censuses are available in a number of datasets in Explore Census Data.