2010 Census - US population - 308,745,538, a 9.7% increase from 2000
2000 Census - US population - 281,421,906
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.
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.
1970 - The population of Hispanic individuals, of any race, is comprehensively counted for the first time.
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.
March 28, 2018 - The NAACP files a lawsuit maintaining that the Census Bureau is underfunded for the 2020 census, which it contends will result in an undercount.
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, files a lawsuit challenging the addition of the citizenship question.
October 22, 2018 - The Supreme Court blocks a deposition of Wilbur Ross, the commerce secretary, in the federal court case challenging the citizenship question.
January 15, 2019 - A federal judge in New York strikes down the proposal to reintroduce a citizenship question.
February 1, 2019 - The Census Bureau announces that it will move forward with plans to test a citizenship question in a nationwide survey midyear, while federal courts weigh the legality of the question.
February 15. 2019 - The Supreme Court announces that it will take up a case involving the citizenship question.
March 6, 2019 - A federal judge in California issues an opinion blocking the citizenship question.
April 1, 2019 - Associate Census Director Al Fontenot says the bureau has prepared two versions of the paper and electronic survey for 2020. One version includes the citizenship question and one version doesn't have the question. Separately, President Donald Trump expresses frustration with the the ongoing litigation, tweeting that the count would be "meaningless" and a waste of money without a citizenship question.
April 2, 2019 - American FactFinder, the Census Bureau's data dissemination tool, is being retired on March 31, 2020, after almost 20 years. A new centralized approach to data dissemination is introduced via data.census.gov.
April 5, 2019 - A federal judge in Maryland issues a 119-page opinion blocking the citizenship question.
April 23, 2019 - The Supreme Court hears oral arguments in the citizenship question case.
June 27, 2019 - The Supreme Court issues a 5-4 ruling that blocks the citizenship question from being added to the 2020 Census. In response, Trump tweets that he has asked lawyers whether the census can be delayed until the government provides the Supreme Court with additional information to make a "final and decisive decision." The narrow ruling does not preclude the bureau from asking about citizenship. It just prevents the bureau from asking in the manner that was presented to the court.
July 2, 2019 - The Trump Administration says it will not ask about citizenship on the census. In a statement, Ross says the bureau is printing census forms without the question, explaining that he respects the Supreme Court but disagrees with the ruling.
July 3, 2019 - Trump tweets that the Commerce Department is actually moving forward on the citizenship question, although he doesn't detail next steps. He describes news reports of dropping the citizenship question as incorrect and fake.
July 11, 2019 - Trump issues an executive action directing the Commerce Department to obtain citizenship data through other means, tabling his effort to add a question about citizenship status to the 2020 Census, setting aside his demands last week to continue pursuing the issue despite a Supreme Court order blocking it.
July 16, 2019 - New York Federal Judge Jesse Furman issues order definitively blocking the Trump administration from adding a citizenship question to the 2020 census in any form.
March 18, 2020 - The Census Bureau suspends 2020 Census field operations for two weeks to protect the health of its employees and the public during the coronavirus pandemic.
March 27, 2020 - The Bureau announces that, as of March 20, in-person Census 2020 interviews are eliminated to slow the spread of the coronavirus, although field workers may telephone participants "where feasible."