The cause of the Great Depression was economic failure after the stock market crashed on October 29, 1929. This was so devastating to many Americans because most of them had bought products on an installment plan and had invested in the stock market, so they weren't able to pay off the rest of the money on say a new car. When they went to take money out of the bank, they would have found that the banks had invested their patron's money in the stock market and hundreds of banks failed for that reason. People were evicted from there homes and had to sell their belongings to keep themselves alive.