What factors led to the crash of the stock market in 1920's?

Over-speculation in the stock market.Loose controls over buying stocks on margin.Underlying economic weakness in farming and some industries.Over-extended consumers living beyond their means by using easy-to-get credit.Tightening of credit that started in early 1929.

There was over speculation in the Stock Market, which was not regulated. Many Americans purchased stock on credit. This was known as margin buying. Many stock-owners didn't even take the time to investigate before they invested in a company. It was felt that all prices would go up, regardless of the nature of the company. Many companies existed on paper only. Prices for stock and the value of the company were not regulated nor checked by the government or the Stock Market. When the economy started to turn downward, the stock brokers called in their margin credit, and most people did not have the money on hand. They tried to sell their stock to pay off the margin but prices kept going lower and there were no buyers. The Stock Market collapse signaled how weak the economy actually was.