"A census is a count of the population of a country at a fixed date. National governments conduct censuses to determine how many people live in a different areas of the country; to assess whether or not the population is growing, stable, or declining in the country as a whole, & in particular parts of the country; & to describe the characteristics of the population in terms of age, sex, ethnic background, marital status, income & other variables." (Encyclopedia of the U.S. Census, p. ix.)
The first census of the United States was in 1790. The U.S. Census Bureau conducts a census of the population every 10 years.