Black Tuesday, the climax of the 1929 Wall Street Crash, occurred on October 29, 1929.
On that Tuesday, investors traded roughly 16 million shares on the New York Stock Exchange, an extraordinary volume for the period. Prices collapsed as widespread selling overwhelmed demand, following major declines on Black Thursday, October 24, and Black Monday, October 28.
The crash did not by itself create every condition of the Great Depression, but it severely damaged confidence, reduced wealth, and weakened businesses and banks. The Dow Jones Industrial Average eventually fell nearly 89% from its September 1929 peak to its July 1932 low.
Black Tuesday is sometimes confused with Black Thursday, the first dramatic selling day in the 1929 sequence. The two dates were part of the same historic market breakdown, but October 29 is the standard answer for the crash's most famous day.