Censuses can be used to find more than simply the address of an ancestor in a certain year. Here’s some general information about the decennial U.S. census, with specific details about the 1920 census.

The first federal census was in 1790, under Secretary of State Thomas Jefferson. There have been 22 since then, taken at 10-year intervals. The last was in 2010. Censuses from 1790 through 1930 are available online and in hard copy at many sources.

Excluded is the 1890 census, most of which was destroyed by fire. For privacy reasons, availability was limited after 1930; however, the 1940 census is expected to be released this April.

The questions asked varied between censuses, from simple identification and place of residence in the first to much more detailed information in later versions. An image from the 1920 U.S. census can be seen on Wikipedia. That census collected the following information:

• Address
• Name
• Relationship to head of family
• Sex
• Race
• Age at last birthday
• Marital status
• If foreign born, year of immigration to the U.S., if naturalized, and year of such
• School attendance
• Literacy
• Birthplace of person and parents
• If foreign-born, the mother tongue
• Ability to speak English
• Occupation, industry, and class of worker
• Was home owned or rented: if owned, was it mortgaged

Before considering individual listings, note the township, county, and state where the census was taken. You can contact churches, courthouses, or public offices in those localities for other records: naturalization, birth, death or marriage records, etc.

Address: Be sure to distinguish between house number (address) and the sequence number indicating the order in which the census was taken. Street names and house numbers allow location of the actual property where your ancestor lived and can lead to churches, cemeteries, local funeral homes, schools, etc., to search for other records.

Name: Remember that to search online or digitized census records by name, you may have to use innovative or imaginative spellings of the name. Usually the head of household’s given name and surname are listed, with only given names for the rest of the family.

Relationship to head of family: Study the family members’ names and relationships to the head. A woman with a different surname than the head may be listed as “mother-in-law,” thus giving you the “maiden” surname of the wife of the head of household. When a surname listed for a “daughter” is different from that of the head, it’s the married surname of the daughter.

Sex: Errors here are not uncommon. Young children with “foreign-sounding” names may have been attributed the wrong gender. So your grandfather Andrea may have been incorrectly listed as a girl or your aunt Carmen as a boy! Use information from the census as a guide, not as gospel.

Ages given are the person’s age at last birthday. Children’s ages are often given as years and fractions: 4 7/12 means the child was 4 years and 7 months old at the time. The date when the census was taken is at the top of the page, and by subtraction, the approximate year of birth can be calculated.