Someone posted a thread earlier about the top ten most successful businesses during the Great Depression. Someone else pointed out that most of these businesses benefited mainly from WWII, part of the Military Industrial Complex, etc.

My question is besides investing heavily in the Military Industrial Complex, who became millionaires in the 1930s and how did they do it? In other words who went from rags to riches during this period? I'm sure some (maybe most if not all?) of the millionaires held gold during this period.