United States Census: Online and Print sources for the United States Census: Census and ACS online

Beginning in 1940, the decennial census began to incorporate sampling procedures to collect supplementary data (released as supplementary reports of various kinds).

In 1960, the census was conducted using a short form, asked of every household, and a much longer, two-part form, asked of 20% of households.

By 1970, a short form went out to every household, and the long form, sample data, was asked of 1-in-6 households.

1980 - 2000:

In 1980, this data began to appear in tape files, SF1 and SF3.

• SF 1 -- Data is from the short list of questions asked of every household

• SF 3 -- Data is from a much longer, more detailed, list of questions asked of  1-in-6  households.

2010 - the present:

• Decennial Census: A brief questionnaire is sent to every household. More detailed data is available from the American Community Survey (ACS).

• American Community Survey: The ACS is a continuous, rolling, survey of 1-in-8 households. Data is released in 1-year, 3-year*, and 5-year estimates.

*ACS 3-year estimates have been discontinued.

See: Comparing ACS data

• Social Explorer
  • 1790 -
    Includes data from the Decennial Censuses (back to 1790), the American Community Survey (2005 --), along with other datasets not derived from the census, such as religion data (back to 1980).
    Note: Social Explorer does not include the non-decennial (intercensal) data from 1790 to 1945, generally known as the "Dubester set" (referencing a guide issued by the Library of Congress).
    Prior to 1980, you may find that some areas are represented only by numeric codes. To identify the correct code see the census tables for metro-micro areas.
  • From 1940 - 1960:
    Social explorer only provides census tract, county, state and US. See: Print and PDF Sources of Older Census Volumes.
  • 1970 - 2010, reallocated to 2010 census boundaries
  • U.S. Decennial Censuses on 2010 Geographies provide reallocated data from Decennial Censuses on 2010 geographies. "Reallocation of decennial census data on 2010 geographies was performed using reallocation fractions from Longitudinal Tract Data Base (LTDB). Data is available on census tract, county, state and nation level geographies. The form of this survey, as well as the datasets and tables it contains, is kept similar to our corresponding Decennial Census surveys. See: Reallocating Census Data: How Social Explorer Makes Cross-Decade Comparisons Possible.
• National Historical Geographic Information System (NHGIS)
  • 1790 -
    The National Historical Geographic Information System (NHGIS) provides free online access to summary statistics and GIS boundary files for U.S. censuses and other nationwide surveys from 1790 through the present. Includes some geographies not represented in Social Explorer, above.
• Geolytics CDROM
  • 1960 - 2010
    Note: The NCDB (National Change Database) disk includes 1970 - 2010 data, normalized to 2010 boundaries, down to the tract level. Unfortunately, Geolytics, a proprietary company, does not share it's methodology. Compare with Social Explorer Reallocated tables, above. See also: Validating Population Estimates for Harmonized Census Tract Data, 2000–2010 comparing NCDB with LTDB and NHGIS
• Data.Census.Gov
  • 2010 -
    2010 decennial census (short form, sent to every household) and sample data from the American Community Survey (1-year, and 5-year estimates.).

In the very early years, some geographies smaller than county, state, and tract, are not available in Social Explorer. You may be able to find these smaller geographies in print reports for the older decennial censuses or in the National Historical GIS (www.nhgis.org)

An example is the Standard Metropolitan Statistical Areas for 1960 (or places for 1980).

In addition, Social Explorer does not include the non- decennial (intercensal) data from 1790 to 1945, generally known as the Dubester set (referencing a guide issued by the Library of Congress).