The latest video in our Principles of Macroeconomics course at MRUniversity covers Understanding the Great Depression. I like this video a lot. It starts by illustrating the great fall in aggregate demand using the AD-AS model but also looks at the dust bowl, the Smoot-Hawley tariff and the National Industrial Recovery Act (NRA). The section on the tariff beautifully illustrates the argument that trade is like a technology that allows us to almost-magically transform one good into another. And the final section on the awful NRA has some great visuals.