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Census Data and Information

Why the Census

Why is the Decennial Census taken?

The census is used to:

  • determine apportionment of Congressional representatives
  • used to help with transportation planning
  • identify needs for childrens' services
  • distribute funds for community development.

How is it taken?

Traditionally the census is taken using two different forms. They are the:

  • "Short-form" is sent to every household in the United States and asks basic questions that cover relationship to head of household, type of dwelling, sex, age, and race
  • "Long-form" is sent to a percentage of the population and asks more in-depth questions, for example, educational attainment, ethnic origin, and income.
The 2010 Census only had a short form because the decennial long form has been replaced by the American Community Survey (ACS).

Measuring America: The Decennial Censuses From 1790 to 2000 contains copies of the census questionnaires used from 1790 to 2000.

What kind of information is collected?

The decennial census gathers demographic information of the population. Historically, other types of information have been collected about areas such as agriculture, mining, or manufacturing. Now, many of those areas are subjects of their own censuses (e.g. Agriculture, Economic, Governments) or surveys.

Geography of the Census

The basic geographical areas that have been measured over the years include the nation, states and counties.

Census tracts, the smallest geographical unit measured, were created for select cities in 1910, but not included in census publications until 1940.

In 1990, census tracts were expanded to cover all counties; prior to that they covered only metropolitan and other heavily populated areas.

Maps of census blocks and tracts can be found with the decennial census publications.

It is important to note that only data from the short-form is available at the census block level.

More detailed data can be found at the block group level. More information on census geography can be found in the Geographic Areas Reference Manual.


Census Bureau Geographic Hierarchy
Source: U.S. Census Bureau, Geography Division