A census is a government-sponsored enumeration of the population in a particular area and contains a variety of information — names, heads of household (or all household members), ages, citizenship status, ethnic background, and so on. Here are some different types of census records you are likely to come across in your research.

U.S. federal census is also called a population schedule. Federal census records provide the building blocks of your research, allowing you to both confirm information and to learn more. Compiled in the United States for every decade since 1790, census population schedules are comprehensive, detailed records of the federal government's decennial survey of American households. Information from the schedules is used by the federal government for demographic analysis.

The schedules themselves, of interest primarily to genealogists, contain the personal information of the survey respondents. To protect the privacy of the people whose names appear in each schedule, census records are restricted for 72 years after the census is taken and are not available to researchers during that time.

What you will find

The earliest census records contain information on people born well before the American Revolution, while the 1940 schedules — the most recent ones open to public inspection — contain information on many people who are still living. Using these records, a researcher might conceivably trace a family line from a living person down to an ancestor born more than 250 years ago.

From 1790-1840, only the head of household is listed, along with the number of household members in selected age groups. Beginning in 1850, the name of every household member was recorded, along with their age, color, occupation and place of birth. As other census were taken, additional questions were added.

From the 1850 census on, the names, ages, occupations and birthplaces (country or state only) of each member of a household were included.

The 1870 census gave, in addition to previous information, the month of birth if born during the year, the month of marriage if married within the year, and whether the father or mother of each individual was foreign born.

The 1880 census (and later censuses) added two valuable pieces of information: the relationship of each person to the head of the household and the birthplace of the father and mother of each person.

The 1885 census was a special census, with population and mortality schedules conducted by the federal government to help five states or territories — Colorado, Florida, Nebraska, New Mexico and the Dakota Territory.

The 1890 census was largely destroyed by fire in 1921 and only fragments of it are available.

The census 1900 and 1910 asked the questions on the 1880 census, according to Familysearch.org, but also include the age of each individual, how many years he had been married, his year of immigration, and his citizenship status. The 1900 census also gives the month and year of birth. "For mothers it lists the number of children born and surviving. The 1910 census identifies Civil War veterans."

"The 1920 census includes the same information as was found on the 1910 census. It gives ages but not the month and year of birth. It also lists the year of naturalization, the only census to do so," Familysearch.org says.

The 1930 census asks questions on the 1920 census and also asks for marital status and, if married, age at first marriage, according to FamilySearch.org. If the individual was an American Indian, it asks whether he or she is "full blooded or mixed blood" and for tribal affiliation.

The 1940 census included several standard questions, such as name, age, gender, race, education and place of birth. But the census also introduced some new questions. The instructions ask the enumerator to enter a circled x after the name of the person furnishing the information about the family. It also asked whether the person worked for the CCC, WPA or NYA the week of March 24-30, 1940; and asked for their income for the 12 months ending Dec. 31, 1939.

The 1940 census also has a supplemental schedule for two names on each page. The supplemental schedule asks the place of birth of the person's father and mother; the person's usual occupation, not just what they were doing the week of March 24-30, 1940; and for all women who are or have been married, whether this woman had been married more than once and age at first marriage.

Editor's note: The original version of this story posted on May 11, 2013 failed to properly attribute all source materials, which violates our editorial policies. The story was revised on March 18, 2014 and attribution to original sources were added.

Barry J. Ewell is author of "Family Treasures: 15 Lessons, Tips, and Tricks for Discovering your Family History," and founder of MyGenShare.com, an online educational website for genealogy and family history.