What is a census?
A census is an exercise in which an entire statistical population is counted.
Barr, R. (2004). Census. In Michael S. Lewis-Beck, A. Bryman, & Tim Futing Liao (Eds.), The SAGE Encyclopedia of Social Science Research Methods. (pp. 111-113). Thousand Oaks, CA: Sage Publications, Inc. doi: http://dx.doi.org/10.4135/9781412950589.n106
What is a statistical population?
A “statistical population” of a census can count objects beyond people. It could include: businesses, houses, cars, farmers, crops, jails etc…
population. (2004). In Duncan Cramer, & D. Howitt (Eds.), The SAGE Dictionary of Statistics. (p. 129). London, England: SAGE Publications, Ltd. Retrieved from http://srmo.sagepub.com/view/the-sage-dictionary-of-statistics/SAGE.xml
Consequently there are many US Censuses you could exlore:
Who are my relatives?
More often than not, though, people talking about the census are referring to the decennial Census of Population and Housing which collects all sorts of information about people and households in the United States, Puerto Rico, and the Island Areas [American Samoa, the Commonwealth of the Northern Mariana Islands, Guam, and the U.S. Virgin Islands].
Officially, the Census of Population and Housing is taken for the purpose of legislative apportionment and redistricting. Changes can affect the level of federal assistance available to a census geographic area and its population as well as the number of representatives an area may send to Washington.
Personal information is not released until 72 years after the decennial census is taken. However, because this information does become available, the decennial census is a primary source for genealogists and family historians. Taking you back to the 1940s is the Web site for the Census Bureau's latest release of personal information from the census.
Scope of this guide
This guide is designed to assist you in finding resources that provide summaries and visualizations of the data or number counts. It also will direct you to resources that will allow you to download data to create your own analysis.
Census geography can be quite confusing for the novice. The Census Bureau has produced a number of videos and presentations that can help you understand terms like tract, blocks, or consolidate government. As well as the history of these geographic units.