The decennial census is the only data gathering operation in the United States that is mandated by the Constitution. The first census was taken in 1790 and has continued every 10 years, in the years ending in "0".
Its primary purpose is to provide the population counts that determine how seats in the U.S. House of Representatives are apportioned. Census figures also are required to draw congressional and state legislative district boundaries, to allocate federal and state funds, to formulate public policy, and to assist with planning and decision making in the private sector.
Census Data File Descriptions:
Summary File 1 (SF 1) contains data on age, sex, households, families, and housing units based on answers to the questions common to both the Census 2000 Short-Form and Long-Form Questionnaires. [Census 2000] Age, Hispanic or Latino Origin, Household Relationship, Owners and Renters, Race, Sex, and more...
Summary File 2 (SF2) contains 47 detailed tables focusing on age, sex, households, families, and occupied housing units for the total population. These tables are repeated for 249 detailed population groups based on the following criteria:
* no tables are available for geographic areas having a population of less than 100
* tables are repeated only for the race groups, American Indian and Alaska Native tribes, and Hispanic or Latino groups having a population of 100 or more within the geographic area.
Summary File 3 consists of 813 detailed tables of Census 2000 social, economic and housing characteristics compiled from a sample of approximately 19 million housing units (about 1 in 6 households) that received the Census 2000 long-form questionnaire. Fifty-one tables are repeated for nine major race and Hispanic or Latino groups: White alone; Black or African American alone; American Indian and Alaska Native alone; Asian alone; Native Hawaiian and Other Pacific Islander alone; Some other race alone; Two or more races; Hispanic or Latino; and White alone, not Hispanic or Latino. Data on Ancestry, Citizenship, Disability, Educational Attainment, Income, Industry, Language Spoken at Home, Marital Status, Migration, Occupation, Place of Birth, Place of Work, Poverty, Rent, School Enrollment, Tenure, Units in Structure, and more...
Summary File 4 contains tabulations of population and housing data collected from a sample of the population. The data are shown down to the census tract level for 336 race, Hispanic or Latino, American Indian and Alaska Native, and ancestry categories.