A great Census Bureau infographic summarizes some information on how America has changed since the 1940 Census. I liked this picture of the shrinking workforce. I think a lot of people don't recognize how prominent agricultural labor still was in the 1930s. On the one hand, this drives home the fact that the initial exclusion of agricultural workers from Social Security was a really major compromise.
On the other hand, it helps us understand the different political economy of the New Deal era versus our own. Probably the most effective policy measure the Roosevelt administration undertook to promote recovery from the Depression was breaking the link of the dollar to gold combined with a self-conscious drive to raise the price level. That was easier to sell to the public when a large share of the population was engaged in primary commodity production, and when a great deal of the service economy must have had agriculutral workers as their primary clients.
I was personally interested to learn that not only manufacturing and agriculture but also retail trade have shrunk as a share of the workforce over the past 70 years.