The U.S. stock-market collapse on 29 October 1929 is called Black Tuesday.
Black Tuesday followed Black Thursday (24 October) and Black Monday (28 October) during the Wall Street Crash of 1929. On 29 October, investors sold roughly 16 million shares on the New York Stock Exchange, overwhelming buyers and sending prices sharply lower. The Dow Jones Industrial Average dropped about 12 percent that day.
The crash did not by itself create every problem of the Great Depression, but it destroyed wealth, damaged confidence and exposed weaknesses in heavily leveraged speculation. Bank failures, falling production and unemployment deepened afterward. Black Tuesday is sometimes confused with Black Thursday, the first dramatic sell-off of that week, or with the broader Wall Street Crash, which lasted from 1929 into the early 1930s.