The U.S. Decennial Census of Population & Housing is the most comprehensive demographic survey in the United States. It is mandated by the U.S. Constitution for the purposes of Congressional apportionment, and has taken place very 10 years since 1790. What questions were asked and the methods of gathering data have changed over time, but the Census gives us a window into the demographic nature of the U.S. population at a given moment in time. It is highly useful for tracking change in communities over time, as well as general population trends, or providing a detailed economic, social and housing profile of a geographic place.
How do you find out what's in the Census? Find out what questions were asked!
Questions change from Census to Census (sometimes dramatically) which means that the statistics available change from decade to decade. The easiest way to find out what information is available for a specific Census is to look at the Census questionnaires. If the question wasn’t asked, the information isn’t available. It’s that simple. For copies of the original Census Questionnaires from 1790 to 2000, see the Census publication Measuring the Census: The Decennial Censuses from 1790 to 2000. It is available in print: Locust Street Facility C 3.2:M 46/2 and online from the Census Bureau. The 2010 Census Questionnaire is available online and coming in at only 10 questions, is the shortest Census questionnaire of the 20th Century.
The Books & Reference Sources below are useful for learning more about how to use the Census and what statistics are available for specific years. Even older reference works will include useful information on what the Census is and how to use it.