According to Wikipedia the most famous book on the depression, Friedman and Schwartz's A Monetary History of the United States, 1867–1960 offers a single cause

According to Wikipedia the most famous book on the depression, Friedman and Schwartz's A Monetary History of the United States, 1867–1960 offers a single cause for the great depression, falling money supply. That might be right or wrong, I don't know. But I know that Housel's "it was a lot of things" is lazy thinking that sounds like wisdom.