How To Find Supplemental Census Questions (1940 Census)

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What are “Supplemental Census Questions?” Did you know that the one major thing that changed between the US Census of 1930 and 1940 was the elimination of the ‘NATIVITY OF PARENTS’ section for all respondents? For genealogists this is a huge blow and creates a dearth of data for researchers to work with in this time period; however, it is a little known fact that on the 1940 Census there still was a section that recorded the ‘Nativity’ (birth places of parents) for a pre-selected few. These were a part of the “supplemental questions.”

When I say “pre-selected” I mean there were designated lines indicating who got asked these questions; if you weren’t on one of those lines, your information was not recorded. When I say “a few” I mean only 5% of the total population included in the Census data got asked these supplemental questions.

Here’s how to find those ‘supplemental census questions’ on the 1940 Census. Each form of the 1940 Census contained enough lines for 40 entries per page, there were two pages per form. The first page ran from 1-40 and the reverse side contained lines 41-80, the forms were double-sided. TWO people from each side of the page were pre-selected to be asked these ‘supplemental questions’ by the enumerators; a TAB that was printed onto the form indicated which person was to be that respondent. It was completely at random, it could be the head of a household, a spouse, or a child and all depended on how the list progressed (was filled out) downward from the top of the page.

MATH: 2 ÷ 40 = 0.05. Times that by 100: 0.05 × 100 = 5.0%. Voila! 5% of the population.

This Ancestry screenshot (and the one below it) is actually my grandfather’s; however, just to illustrate the random nature of these pre-selections, line 55 landed on a 2 year old kid and therefore did not contain much information overall. You can see it says “SUPPL. QUEST.” in the margin – if your census has that, it’s money.

"Suppl quest" on Ancestry census — source: ancestry (modified)

The supplemental census questions included:

Name
Place of Birth of Father (Nativity)
Place of Birth of Mother (Nativity)
Mother Tongue (Native Language)
4 Veterans questions
3 Social Security questions
3 Usual Occupation, Industry, and Class of Worker questions
3 “For All Women Who Are Or Have Been Married” questions
A section For Office Use Only

bottom of the 1940 census — supplemental questions section. source: ancestry (modified)

For a full list of questions asked on the 1940 Census, visit the US Census Bureau’s page for this census. This list does NOT include the supplemental questions, however.

There are 2 ways to find all of the supplemental questions via Ancestry.com. The FIRST is to simply scroll down on the 1940 Census which will bring the supplemental questions into view – pictured above. You will first need to look for the “SUPPL. QUEST.” tab in the margin of the census page to see which respondent the questions correspond to. The SECOND way is to click on the “Show Index” button at the bottom of the page while viewing the 1940 Census. This will load all the questions and fields into a slider window which you will then need to scroll all the way to the right to find.

1940 census "suppl quest" — source: ancestry (modified)

Ancestry tab for census — source: ancestry (modified)

Once this slider window is open you will be able to view all of the information that was enumerated for this person in the household – again, you will have to scroll all the way right. In my grandfather’s case, it was his first-born son who was only 2 years old at the time! Sufficed to say that his father (my great-grandfather) was answering all of the questions on his behalf. That is the random nature of the way this census dealt with the ‘Nativity’ question; it’s kind of a shame, really, as having the birth places listed for everyone on the census was an absolute gold mine for genealogists and family historians.

supplemental questions on Ancestry — supplemental questions index. source: ancestry (modified)

If you see that tab (“SUPPL. QUEST.”) attached to any of your family on a 1940 Census make sure you include that in your research of you haven’t already. If you are used to viewing the 1910, 1920, and 1930 Censuses you may not have even been aware that there were supplemental questions in the first place so it may behoove you to go back over your Ancestry tree and review those that fall within the scope of the 1940 Census.

The US Census Bureau has put out a very informative PDF publication which I would highly recommend reading. It is an overview of how all of the Censuses were handled, from the very first in 1790 up until 2000, in a publication entitled “Measuring America: The Decennial Censuses From 1790 to 2000” (published in 2002). It’s worth a read-through as it contains volumes of census snapshots, instructions for the enumerators, as well as insights into what the differences were between each of the census years covered.

Learn more about how to research Censuses, City Directories, and Street Guides in my article 10 Tips For Researching City Directories and Street Guides.

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