How to Read the U.S. Federal Census (1790–1950)
What each federal census asked, which years are most useful, and how to get every clue out of a census page.
The federal census has been taken every ten years since 1790, and it is the backbone of American genealogy. Records are released to the public 72 years after the count, so 1950 is the most recent census you can search today. The 1960 census is scheduled for release in 2032.
Two eras: before and after 1850
1790–1840 censuses name only the head of household. Everyone else is a tick mark in an age and sex column. They are still useful: you can sketch a family's makeup and follow it across decades, but you can't prove relationships from them alone.
1850 onward names every free person in the household with age, sex and birthplace. This is where most beginners make their first big breakthroughs.
What changed, census by census
| Year | Key new details |
|---|---|
| 1850 | Every free person named; age, birthplace (state or country). Separate slave schedules list enslaved people by age and sex, usually without names. |
| 1860 | Similar to 1850, plus the value of personal property. |
| 1870 | First census to name formerly enslaved people. Notes whether parents were foreign-born. |
| 1880 | Relationship to head of household, and each person's parents' birthplaces. |
| 1890 | Almost entirely destroyed after a 1921 fire. Use the 1890 Veterans Schedule and state censuses instead. |
| 1900 | Month and year of birth, years married, number of children born and living, year of immigration. |
| 1910 | Similar to 1900; asks about Union or Confederate veterans. |
| 1920 | Year of naturalization; mother tongue. |
| 1930 | Age at first marriage, radio ownership, veteran status. |
| 1940 | Where each person lived in 1935, highest grade completed, income. |
| 1950 | Detailed questions for a sample of people on each page. |
Read the whole page, not just your family
Census takers walked door to door, so the people listed before and after your family were their actual neighbors. Relatives often lived nearby: married daughters, in-laws, a widowed grandmother next door. Researchers call studying these neighbors cluster research or the "FAN club" (Friends, Associates and Neighbors). It is one of the most powerful techniques in genealogy.
Expect errors
Ages drift, names get misspelled, and the person answering the door might have been a child or a neighbor. Don't throw out a record because one detail is off. Look at the whole household and compare across several census years. If names are badly misspelled in an index, search by first name, age and place instead of surname.
Don't forget state censuses
Many states took their own censuses in years ending in 5 (1855, 1865, 1875 and so on). They fill gaps between federal counts and are especially valuable for the missing 1890 years. Check the state guide for your ancestor's state to see what survives.
Next: Finding Ancestors Before Statewide Vital Records →