I was doing research on Ancestry.com, and my dad’s 1930 and 1940 census forms are on there. The citizenship question was on the form, but not one person on the page that he appears on was actually asked the question. That question is blank all the way down the page.
Sometimes it’s obvious a person is a citizen. Census takers back then had to get through it all in a hurry. That caused the forms to later be split into long and short forms.
Back then there also wasn’t the fraud and invasion we have today.
I’m thinking what Hostage is thinking - that the boxes were left blank for citizens.
I have 1920 forms for my ancestors. For my ancestors who were immigrants, the citizenship boxes are filled in. For their children who were born here, the citizenship boxes are left blank.