The questions asked on the Census form reflect trends in American society and the economy. Therefore, they have evolved considerably over the years. For example, in the first few Census counts, data was gathered on how many slaves or indentured servants were attached to a household. That question disappeared after the U.S. Civil War.
... the first inquiry on manufactures was made in 1810; it concerned the quantity and value of products. Questions on agriculture, mining, and fisheries were added in 1840; and in 1850, the census included inquiries on social issues—taxation, churches, pauperism, and crime.. - excerpt from Factfinder for the Nation: History and Organization. (May, 2009). http://www.census.gov/history/pdf/cff4.pdf
Even in the 21st century, Census questions continue to change. Racial categories have evolved and changed definition from year to year, in accordance with social trends. For most of the Censuses, people had to select a single racial or ethnic category to define themselves. In 2000, for the first time, people were allowed to self identify themselves as one or more races, an acknowledgement of America's growing multiculturalism. Data on same-sex couples was included in the recent 2010 Census, mirroring advances in gay rights in the decade since 2000.
To explore the questions asked on the Census forms for each year, refer to Through the Decades, Index of Questions and see how the questions asked provide clues to the issues and trends in American society at that time.
Early Census forms were short and simple, gathering only basic demographic data. Over the years, the Census expanded to include more questions, as the country itself expanded and the population grew and became more diverse.
Since the first census in 1790, the U.S. Census Bureau has collected data using a census "schedule," also called a "questionnaire." Between 1790 and 1820, U.S. Marshals conducting the census were responsible for supplying paper and writing-in headings related to the questions asked (i.e., name, age, sex, race, etc.). In 1830, Congress authorized the printing of uniform schedules for use throughout the United States.
The 1940 Census included separate questionnaires to count the population and collect housing data. The 1960 and later censuses combined population and housing questions onto a single questionnaire mailed to households or completed during a census taker's visit.
Between 1970 and 2000, the U.S. Census Bureau used two questionnaires. Most households received a short-form questionnaire asking a minimum number of questions. Only a sample of households received a long-form questionnaire that included additional questions about the household. The data from the long form are called “sample data.” The basic data collected on both the short and the long forms are called “100 percent data” since these questions were asked for 100 percent of the U.S. population.
The 2010 Census only used a short form questionnaire consisting of ten questions (see below). Questions previously asked on the long form are now part of the American Community Survey (ACS).
Beginning with the 2010 Census, only one census form was distributed to U.S. households, the Short Form, which asked only 10 questions from the following categories:
Hispanic or Latino origin
Tenure (whether the home is owned or rented)