Black Tuesday, October 29, 1929, was the most famous single day of the Wall Street Crash of 1929.
Investors sold roughly 16 million shares on the New York Stock Exchange, then an unprecedented volume. The Dow Jones Industrial Average fell about 12.8 percent that day, following large declines on Black Thursday, October 24, and Black Monday, October 28.
The crash did not by itself create the entire Great Depression. The subsequent economic collapse also involved bank failures, falling prices, reduced production, unemployment, and policy mistakes. The Dow continued falling after October 29 and reached its bear-market low in July 1932.
A common mix-up is treating Black Tuesday as the beginning of the crash. Selling had already become severe several days earlier, but October 29 became the enduring symbol because of its enormous trading volume and dramatic losses.