The final major Wall Street sell-off of October 1929 is most closely associated with Black Tuesday.
Black Tuesday occurred on October 29, 1929, when panic selling overwhelmed the New York Stock Exchange. About 16 million shares changed hands, a record at the time, and the Dow Jones Industrial Average fell roughly 12%. The collapse followed Black Thursday on October 24 and a temporary rebound supported by leading bankers.
The crash did not single-handedly cause the Great Depression. Economic contraction, banking failures, falling demand, debt, and international financial problems all played important roles. However, the stock-market collapse destroyed wealth and confidence and became the era's defining financial symbol.
Black Tuesday is often used loosely for the entire 1929 crash, but the market decline unfolded over several days and then continued for years. The Dow ultimately reached its low in July 1932, far below its September 1929 peak.