I've been tweeting a Census history series lately, reporting on one decennial census each day through census day (April 1). I got to 1940 today and found three promotional films posted on YouTube. They encourage 1940s USians to be counted as a civic and patriotic duty.
Let me recommend the Census Bureau's Through the Decades web site, it makes fascinating reading. I particularly enjoy the scanned historic Census publications they offer.
And I've been posting a decade-by-decade record of state and county Census counts for Delaware. I'm including links to the scanned publications that cover Delaware.