Beginning in 1790 as required by law, the U.S. federal government began conducting a decennial census, or count of the population, every 10 years. The purpose was to fairly distribute Congressional representation and taxation among the states, which remains its primary purpose to this day. Other questions regarding various social aspects of our society vary from census to census, are not necessarily required, and are only asked of a sample of the population.
In addition to the Census of Population and Housing, other types of censuses conducted by the federal government at various times are agriculture, manufacturing, retail trade, wholesale trade, transportation and government. For some years these were included in with the Census of Population and Housing. More recently though, they are done at seperate times, usually in years ending in 2 or 7.
Individual states have also conducted censuses at various times, including Wisconsin. Typically, state censuses were initially done to determine statehood eligibility and usually were not done after the early 1900s.
A unique census that helps researchers in many fields and for many purposes are school censuses. Typically, these are conducted annually within a school district and record names, actual birthdates, and parents' names. The Archives department holds these for many northeastern Wisconsin schools, most notably Brown County.
Another type of census is the Native American Census rolls conducted by the Bureau of Indian Affairs. Unlike the federal census, the data is not restricted for 72 years. Data in this type of census includes name, reservation, actual residence, family members, birthdates, and blood quantum. In many instances, this census data was annotated years after the original census was recorded thereby providing updated vital records information.
Statistical compilations of data from the census are released to the public, although it may take considerable time for this to happen. For example, the government is still compiling and releasing data from the 2010 census 2 years after it occurred.
The other type of information released is the original census manuscripts that record information about individuals. This type of information is eagerly sought after by family history researchers, scholars, and genealogists. There is a 72 year freeze on the release of personal information from the census. Also, for small geographic areas even statistical data may be withheld from publication to protect the privacy of the individuals involved. Earlier census publications were of course done in paper, while in the latter half of the 20th century, microfiche and then cd-rom formats were used, with current statistics available electronically on the Bureau of the Census website. Our statistical compilations from before 1900 are held in our Archives Department. Statistical publications from 1900 to 2000 are in our 5th floor U.S. Government Publications Collection.
There is a 72 year moratorium on the release of personal information from the census. Researchers around the globe are eagerly looking forward to the release of the 1940 census on April 2, 2012. The 1940 census will not be indexed upon its initial release. It will be browseable by geographic locations but not searchable by individual names. Volunteers will begin indexing names immediately, but there is no target date for completion of the index.
Earlier censuses originally existed in 3 versions, a local (county) copy, a state copy, and a federal copy. The National Archives and Records Administration (NARA) is the custodian of the federal copies, which they have microfilmed. Many state archives have the copy for their state, either on microfilm or manuscript. The local copies rarely survived, but our Archives Department has some of these for Brown County. Although the content should be identical, there may be slight variations between the 3 versions.
It may also help to check multiple electronic versions, since the indexing or images may be clearer in one or the other. Remember also that the majority of the 1890 census was destroyed in a fire.
For more information about the 1940 census see http://www.census.gov/1940census/index.html
To get started with the 1940 census visit http://1940census.archives.gov/
For help in determining your census tract or ed number for a locality, use the finding ads on Steve Morse's website at http://stevemorse.org/