They have also posted the 28-page Myths of the Great Depression report by Lawrence W. Reed.
The four downturns, with Wikipedia links:
1. Monetary Policy and the Business Cycle. See the Wall Street Crash of 1929.
2. The Disintegration of the World Economy. See Smoot-Hawley Tariff.
3. The New Deal.
4. The National Labor Relations Act (NLRA), or the Wagner Act.
Go there to read more. They posted a video there too.