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What is the U.S. Census?

Introduction to Census Records -- from the National Archives website

The name of your relative or ancestor, and the state he or she resided in, is enough to get you started searching Census records.

The first Federal Population Census was taken in 1790, and has been taken every ten years since. However, data from recent censuses are not available after 1940 because of a 72-year restriction on access to the Census. Most researchers find it most helpful to begin with the 1940 Census and work backwards to locate people in earlier generations.

What can the Census tell me?

Census records can provide the building blocks of your research, allowing you to both confirm information, and to learn more.

From 1850 to 1940, details are provided for all individuals in each household, such as:

  • names of family members
  • their ages at a certain point in time
  • their state or country of birth
  • their parent's birthplaces
  • year of immigration
  • street address
  • marriage status and years of marriage
  • occupation(s)
  • value of their home and personal belongings
  • the crops that they grew (in agricultural schedules), etc.
Tip: Begin with the most current census year available and work backwards. With the 72-year restriction on access to the Census, the most current year available is 1940.

Not all of this kind of information is available in every census. Before the 1850 Census, few of these details were recorded. From 1790-1840, only the head of household is listed and the number of household members in selected age groups.

For specifics on what information was collected in each census year, see Availability of Census Records About Individuals

The U.S. Census

Clues in Census Records, 1850-1940

Experienced genealogical researchers use clues found in one record to find other records about the same individual. This article describes some of the clues found in census records.

Date of birth

  • The 1900 census (column 7) indicates the person's month and year of birth; the 1850-1880 and 1910-1940 censuses indicate the person's age.
  • The 1870 census (column 13) and 1880 census (column 7) indicate the month in which the person was born, if born "within the year," that is between June 1, 1869 and May 31, 1870 for the 1870 census, or June 1, 1879 and May 31, 1880, for the 1880 census. The official census day was June 1 in both 1870 and 1880, although the enumerator may have visited the household at a later date.
  • While the person's age is not an exact date of birth, it at least provides a "ballpark" figure useful (1) for tracking the person from one census to the next, especially if other people have the same name, and (2) for locating the person in any existing vital records.

Place of birth

  • The 1850-1940 censuses indicate the person's state or country of birth, which helps narrow the geographic scope of search for the specific town of birth.

Date of marriage

  • The 1850 census (column 10), 1860 census (column 11), 1870 census (column 14), and 1880 census (column 12) indicate whether the person had married within the year.
  • "Within the year" means during the year before the official census day, that is, between June 1, 1849 and May 31, 1850, for the 1850 census; between June 1, 1859 and May 31, 1860, for the 1860 census; between June 1, 1869 and May 31, 1870, for the 1870 census; and between June 1, 1879 and May 31, 1880, for the 1880 census. The official census day was June 1 in each of these census years, although the enumerator may have visited the household at a later date.
  • The 1900 census (column 10) and 1910 census (column 9) indicate the number of years of marriage for each married person.

Number of children

  • The 1900 census (column 11) and 1910 census (column 10) indicate how many children were born to each woman. The 1900 census (column 12) and 1910 census (column 11) indicate how many of those children were still living. These clues can help determine whether the researcher has identified all children in a given family, and whether any were deceased when either census was taken.


  • The 1900 census (column 16), 1910 census (column 15), 1920 census (column 13), and 1930 census (column 22) each indicate the person's year of immigration to the United States. This information should help in locating a ship passenger arrival list.


  • The 1870 census (column 19) has a check mark for "Male Citizens of the U.S. of 21 years of age and upwards." If the person was a foreign-born citizen, this means that he had become naturalized by 1870.
  • The 1900 census (column 18), the 1910 census (column 16), and 1920 census (column 14), and 1930 census (column 23) indicate the person's naturalization status. The answers are "Al" for alien, "Pa" for "first papers," and "Na" for naturalized.
  • The 1920 census (column 15) indicates the year in which the person was naturalized.

    These clues may lead to naturalization records.

Foreign-born parents

  • The 1870 census (columns 11-12) have check marks if the person's parents were "of foreign birth."
  • The 1880 census (columns 25-26), 1900 census (columns 14-15), 1910 census (columns 13-14), 1920 census (columns 21 & 23), and 1930 census (columns 19-20) indicate the person's parents' birthplaces.

Military Service

  • Service in Union or Confederate Army or Navy
    • The 1910 census (column 30) indicates whether the person was a "survivor of the Union or Confederate Army or Navy." The answers are "UA" for Union Army, "UN" for Union Navy, "CA" for Confederate Army, and "CN" for Confederate Navy. These clues lead to military service and pension records; see Civil War Records and Confederate Pension Records for more information.
    • A word of caution: On the 1910 census, columns 30-32 are often "overwritten" with numbers like 2-1-0-0 or 6-9-0-0. These numbers are not the answers for columns 30-32, but were data summaries used by Census Bureau tabulators in Washington, DC, to compile statistical data.
    • The 1930 census (column 31) indicates Civil War veterans with the abbreviation "CW."
  • Military Service, 1898-1918, in Major Wars
    • The 1930 census (column 31) indicates military service in other wars with "Sp" for Spanish-American War, "Phil" for Philippine Insurrection, "Box" for Boxer Rebellion, "Mex" for Mexican Expedition, and "WW" for World War I.

Real property

  • The 1850 census (column 8), 1860 census (column 8), and 1870 census (column 8) indicate the value of real property (land) owned by each person.
  • The 1900 census (column 25), 1910 census (column 26), 1920 census (column 7), and 1930 census (column 7) indicate whether the person owned ("O") or rented ("R") the home or farm.
  • The 1900 census (column 26), 1910 census (column 27), and 1920 census (column 8) indicate whether home and farm owners owned their property with a mortgage ("M") or free of mortgage ("F").
  • The 1930 census (column 8) indicates the value of home, if owned, or the monthly rental, if rented.

    These clues should lead researchers to the county recorder's office or equivalent agency for deeds, mortgages, and property tax records.

Economic data.

  • The 1850 census (column 7), 1860 census (column 7), 1870 census (column 7), and 1880 census (column 13) all indicate the person's occupation. If the answer is "farmer," the researcher should look for information about the farmer's land ownership, crops, and livestock in the agricultural census schedules. If the person was a saw or grist miller, cheese maker, or other "manufacturer," the researcher should check the manufacturing census schedules.
  • Agricultural census schedules exist for 1850-1880; manufacturing census schedules exist for 1820 and 1850-1880.
  • For more information and roll lists of nonpopulation census schedules available as NARA microfilm publications, see Nonpopulation Census Records.


Researchers who use these and other clues in census records will be more successful--and thorough--in their genealogical research.

This essay is adapted from "Clues in Census Records, 1850-1920," The Record, Vol. 4, No. 3 (Jan. 1998): 26-27.

This material taken from the National Archives website at: