1 person found this helpful
Hello Julia -- thank you for posting to History Hub!
The Library of Congress has a research guide on Congressional District Data that points to a variety of U.S. Census Bureau data sources, academic and government sources, and geographic information sources that you might find helpful.
While the U.S. Census Bureau has historical census information on their website -- see the 1950 Overview -- and they have information on their website regarding congressional district voting rates and population characteristics, and citizen voting age population by race and ethnicity for more recent elections, I don't know if they have that information compiled for the 1940, 1950, or 1960. You may want to try contacting the Census Bureau directly.
You're also welcome to explore the National Archives portal for Census Records.
Thank you so much for these suggestions! I'll look around these sites and reach out to the Census Bureau.