Black Tuesday was the name commonly given to 29 October 1929, the biggest selling day of the Wall Street Crash. About 16 million shares changed hands on the New York Stock Exchange, and the Dow Jones Industrial Average fell nearly 12 percent.
The selling followed Black Thursday on 24 October and Black Monday on 28 October. Together, these sessions destroyed confidence in heavily leveraged stocks and marked the most famous phase of the crash. Prices had previously risen dramatically during the speculative boom of the 1920s.
Black Tuesday did not by itself cause the entire Great Depression. Economic contraction, bank failures, falling investment, debt, and policy decisions all contributed to the depression that followed. The crash also unfolded over a longer period: the Dow continued declining until it reached its 1932 low.