The main cause of the Wall Street crash of 1929 was the long period of speculation that preceded it, during which millions of people invested their savings or borrowed money to buy stocks, pushing prices to unsustainable levels. Other causes included an increase in interest rates by the Federal Reserve in August 1929 and a mild recession earlier that summer, both of which contributed to gradual declines in stock prices in September and October, eventually leading investors to panic.

The Wall Street crash of 1929, also called the Great Crash, was a sudden and steep decline in stock prices in the United States in late October of that year. Over the course of four business days—Black Thursday (October 24) through Black Tuesday (October 29)—the Dow Jones Industrial Average dropped from 305.85 points to 230.07 points, representing a decrease in stock prices of 25 percent.