US Census Fast Facts

WASHINGTON - APRIL 01: Forms for Census 2010 are displayed during an event to promote the census at Ben's Chili Bowl April 1, 2010, in Washington. The event was held to encourage DC residents to participate in the census. (Photo by Alex Wong/Getty Images)

(CNN)Here's some background information about the census, a count of US residents that takes place every 10 years. The Census Bureau is part of the Department of Commerce.

2010 Census - US population - 308,745,538, a 9.7% increase from 2000
2000 Census - US population - 281,421,906
    Other Facts:
    The census is mandated by the US Constitution. "The actual enumeration shall be made within three years after the first meeting of the Congress of the United States, and within every subsequent term of 10 years, in such manner as they shall by Law direct." - Article I, Section 2 of the Constitution of the United States.
    Timeline:
    1790 -
    The first census is conducted by US marshals and their assistants at a cost of $44,000. The population is estimated to be 3.9 million. Residents are categorized as free white males 16 years or older, free white males under 16, free white females, all other free persons and slaves.
    1820 - More detailed employment information is gathered, as respondents are asked to categorize their jobs by industry: agriculture, commerce, or manufacturing. A question about the citizenship (number of foreigners within the household who are not naturalized) appears for the first time.
    1850 - Marshals begin collecting "social statistics," including information on taxes, schools, crime and wages.
    1870 - The Census Bureau phases out its slave questionnaire five years after the ratification of the 13th Amendment which ended slavery. A rudimentary tallying machine is used to expedite the count.
    January 1931 - In response to the Great Depression, Congress mandates a special unemployment census to assess the severity of the crisis.
    1960 - The census questionnaire is mailed out en masse for the first time. Computers process nearly all the data.
    1980 - The census begins obtaining information on race via self-identification. Following the 1980 count, 52 lawsuits are filed against the Census Bureau for various reasons, including the undercounting of minorities, the inclusion of undocumented immigrants and operational issues at some Census Bureau offices. Demographic analysis later shows that the census undercounted the population by 1.2% and undercounted African-Americans at a rate 3.7% higher than any other minority group.
    1990 - The Census Bureau introduces a program called S-Night (streets/shelters), a one-night sweep to count the homeless popular in major cities, building on the previous efforts to count itinerant individuals. Many newspapers refer to the S-night as the "homeless census."
    2005 - The Census Bureau begins collecting data for the American Community Survey, an annual survey that lists demographic, economic and housing characteristics for localities with populations of 20,000 or more.
    December 14, 2010 - The first multiyear estimates based on the American Community Survey data are released.
    March 26, 2018 - The Commerce Department announces that the question of citizenship will be reintroduced to the census. The change was requested by the Justice Department, reportedly in the interest of enforcing the Voting Rights Act. The citizenship question was included on most census counts between 1820 and 1950, according to the Commerce Department. Civil rights groups oppose the change because undocumented individuals may opt not to participate if their citizenship is questioned, leaving a significant portion of the population uncounted.
    March 27, 2018 - California files a lawsuit, challenging the addition of the citizenship question in federal court.
    April 3, 2018 - New York's attorney general, along with a coalition of 18 attorneys general, six cities, and the bipartisan US Conference of Mayors file a lawsuit challenging the addition of the citizenship question to the 2020 census.