A lot of Freepers actually believe the Great Depression was caused by an obscure trade bill signed a year AFTER the crash, the Smoot-Hawley Act. A lot of Freepers are historically ignorant.
Speculative stock market bubble, bubble burst, too many buying on margin, debts could not be repaid, banks failed with no safety net, wiping out a lot of people. Money became scarce, causing prices to fall because few could buy. Businesses failed due to declining sales. Rinse and repeat a few years later. The US economy was not export based at the time, nor was it heavily dependent upon imports. Smoot-Hawley may or may not have been ill-advised, but it did not cause the Great Depression.
Hoover signed Smoot-Hawley; Jack French Kemp put forth the view that it worsened the depression.
It was Smooooooooooot. :)