The Wall Street Crash began in 1929, when Black Thursday struck the New York Stock Exchange on October 24.
After years of rising share prices and widespread speculation, investors began selling heavily. Banks and financiers attempted to support prices, but renewed selling followed on Black Monday, October 28, and Black Tuesday, October 29. The Dow Jones Industrial Average fell sharply during those sessions.
The crash did not by itself cause every part of the Great Depression, but it severely damaged confidence, reduced wealth, and contributed to falling investment and consumption. Banking failures, monetary policies, debt problems, and international economic weaknesses also deepened the downturn.
A common mix-up is treating October 29 as the start of the crash. It was the most famous day, but the crisis had already become visible with the October 24 sell-off.