Locating Census Data

This page will provide some notes about locating U.S. decennial census data for your research projects. You can also email us at ilrref@cornell.edu or stop by the reference suite in Catherwood Library for an individual consultation!

What is the US Census?

  • The US Census, also known as the decennial census, is carried out by constitutional mandate every ten years, with the aim of counting every resident in the country.  The data collected determines the number of senate seats for each state and informs the distribution of federal funds to communities throughout the US.
  • The most recent US census was conducted in 2010.  Questions asked included number of people in the household, and their age, sex and race.
  • The previous census in 2000, included a 'long form' which asked more than 100 questions and was sent to only a percentage of total residents.
    The 'long form' has since been replaced by the American Community Survey, described below.

What is data.census.gov?

data.census.gov is the US Census Bureau's new website to distribute and make available census and survey data.  It was launched in 2019 as a replacement for American Factfinder.  It is a searchable database of data tables and maps containing information from the following census and survey tools.

For a complete list, visit data.census.gov's FAQ page.  From that page, click on "data.census.gov" -> "Data available" -> "What data are available in data.census.gov?"

A note about population counts

The population is "counted" every 10 years via the decennial census. For population counts (total number of persons) between decennial censuses, see: Population Estimates

The decennial censuses (conducted every ten years) and the American Community Survey (ACS), a rolling survey designed to replace the decennial census Long Form, offer a wide variety of tabulations based on the questions asked. See the links above for more information about the data compiled in the decennial censuses and, more recently, in the American Community Survey.

What is the American Community Survey?

  • The American Community Survey, or ACS, is an ongoing survey sent to a rolling and random sample of the US population every year (about 295,000 per month, 3.5 million per year).
  • In addition to basic demographic data, the ACS collects information regarding disabilities, health insurance, education, income, and family, among others. 


Note that data from the ACS are used to make estimates for the greater population. Data are available as follows:

  • 1-year estimates available for states as well as cities, counties, metro areas, and population groups greater than 65,000
  • 1-year supplemental estimates available from 2014-present for areas with populations of over 20,000
  • 3-year estimates were used between 2007 and 2013 for areas with populations of over 20,000
  • 5-year estimates available for all areas
  • To find out when to use 1, 3, or 5-year estimates, go here.

Differences between the Decennial Census and the ACS

Beginning in 1940, the census began to incoporate 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:

  • 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:

Search: Social Explorer , American Factfinder , (Archived data 2000-2010) and Data.Census.Gov .

  • 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

See also: CQ Press Guide to the American Community Survey of the US Census Bureau