Genealogy 101: #17 The 1940 U.S. Census

Introduction: In this article – part of an ongoing “Introduction to Genealogy” series – Gena Philibert-Ortega explains some of the new questions that were added to the 1940 U.S. Census, and provides links to additional information about that census. Gena is a genealogist and author of the book “From the Family Kitchen.

One of the first sources family historians learn about is the census. In April 2012, the U.S. National Archives released the 1940 census records to the public, more than 3.8 million pages, after the mandatory 72-year waiting period. (The first federal census was taken in 1790.)

Through the decades, the information gathered for the census has changed – and those changes can mean rich family history facts for genealogists. As you begin your research using the census, the search for your family should begin with the latest census available and then work backward, documenting previous generations as you go.

The 1940 census is different than earlier censuses. Like some previous census years, the 1940 census records things like name, birth place (state or country), and occupation – but there are other columns of information in the 1940 census that you need to pay attention to.

What Are Some of the Differences You’ll Find in the 1940 Census?

Photo: 1940 census record for Oscar Philibert
Photo: 1940 census record for Oscar Philibert. Credit: FamilySearch ( accessed 23 February 2017), Oscar Philibert, San Antonio Judicial Township, Los Angeles, California, United States; citing enumeration district (ED) 19-627, sheet 9B, line 44, family 197, Sixteenth Census of the United States, 1940, NARA digital publication T627. Records of the Bureau of the Census, 1790 – 2007, RG 29. Washington, D.C.: National Archives and Records Administration, 2012, roll 249.

Census questions change over time and the 1940 census is no different. Some of the changes might be pretty obvious to the family history researcher, and some changes not quite so obvious.

1935 Information Included

One of the big differences you’ll notice in the 1940 census is the addition of questions having to do with where each person lived on 1 April 1935. This allows the researcher to learn more about their ancestor at a 5-year gap, rather than the usual 10-year gap between census information. Even if the person in question is listed as living in the “same house” in 1935, that information – along with the 1930 census – helps you to identify their location for 1930, 1935, and 1940. Continue your documentation of their address in between census years by following up with city directory research.

Informant (Source of Family Information) Identified

One of the problems with census research is that we have no idea how reliable the information is prior to the 1940 census. After all, there’s no indication of who supplied the information for the family. The informant for any given census year could be the head of household, a neighbor, or some unrelated person who is providing their best guess about the family.

But that changes in 1940. In the 1940 census, the informant has a mark to the right of their name, an “x” with a circle around it. Enumerators (census takers) were instructed that, if someone outside the family was the source of the information, then the informant’s name should be written in the left-hand margin.* That system helps us determine the accuracy of our ancestors’ census information.

Supplemental Questions

The bottom of the 1940 census form is different from previous forms. There are supplemental questions found on the bottom of each page. These questions provide more information about the people found on two lines of each page, about 5% of those listed in the census. This extra information includes the place of birth of that person’s father and mother; native language; veteran status; Social Security-related questions including if that person had a Social Security number; and occupation status. In addition, questions for women who were or had been married included whether the woman had been married more than once; age at first marriage; and number of children born to her.

An article about the 1940 census, Repository newspaper article 31 March 1940
Repository (Canton, Ohio), 31 March 1940, page 1

Resources about the 1940 Census

  • To view a list of the questions asked in the 1940 census, consult the National Archives web page Questions Asked on the 1940 Census. This web page also provides the codes used for categories like race, education, citizenship, and military service (these codes can also be found at the very bottom of each census page).
  • I would also highly recommend downloading a blank copy of the 1940 census form to use in transcribing information you find on the census. This can be found on the National Archives 1940 Census web page. This will help you pay extra attention to each piece of information that is listed for your ancestor.
  • You can learn more about the instructions provided to enumerators for the 1940 census by reading the Census Bureau Instructions to Enumerators web page.
  • You can find other 1940 census facts on the websites of the Census Bureau and the National Archives.

* “Frequently Asked Questions,” 1940 Census National Archives ( accessed 22 Feb 2017).


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