From FamilySearch.org
The first U.S. federal census was in 1790 and the census is taken every ten years. The records (through the 1940 census) are available to the public. These counted the population as of the following dates:
- 1790-1820: First Monday in August
- 1830-1900: June 1 (June 2 in 1890)
- 1910: April 15
- 1920: January 1
- 1930: April 1
- 1940: April 1
Each census presents its own set of information. Name (of household head only through 1840) and age are recorded in every census. All should have location information (state, county, city or township) and (as of 1880) street name. These are some of the important changes made to the information recorded:
1790--Simple census, with the name of each family head and the total number of males of age 16 and up, males under the age of 16, number of females, number of slaves and number of all other persons.
1800 to 1840--Name of the head of each household, and only the number of others in the household, male and female, (both by age bands) and number of slaves.
1850 and later--Names, ages, occupations, and birthplaces of each member of a household. Also added is marital status and literacy.
1860--With 1870, the only censuses that reports the value of real estate and of personal property.
1870--With the end of slavery, slave schedules are eliminated, but the recording of race or color would continue. Adds a record whether or not the individual's parents were foreign born.
1880 and later--Adds (in cities) the street name and house number for each household as well as the birthplaces of each person's parents and also reports the relationship of each person to the household head.
1890--with very few (6,190 names) isolated exceptions, these record were destroyed and are lost.
1900-1910--Include how many years married, year of immigration and citizenship status. The 1900 census also gives the month and year of birth (the only census to record both of these). For mothers both of these censuses list the number of children born and surviving. The 1910 census identifies Civil War veterans, Union and Confederate, and also adds more detail to the occupation data.
1920--The 1920 census reports the year of naturalization, the only census to do so.
1930--The 1930 census also asks for marital status and if married, age at first marriage.
1940--The 1940 Census reflects the Great Depression. It reports the place of residence 5 years ago, if at work, whether in private or government work, weeks worked last year, along with wage and salary income last year. Because of this, the parents' birth location is omitted, except as supplementary questions for two random individuals on each page (a page having 40 individuals in total). These two individuals were also asked about their usual occupation and industry (i.e., as opposed to current temporary work or unemployed status).
1950 through 2010--Are scheduled to be released 72 years after the year taken.
Additional Notes:
For much more on U.S. Census records, visit https://familysearch.org/learn/wiki/en/United_States_Federal_Census.
There is also a document showing just the headings for each census from 1790 to 1930 here.
