The 29 October 1929 trading-day crash on the New York Stock Exchange is known as 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 traded roughly 16 million shares, a record at the time, as panic selling overwhelmed the market.
The Dow Jones Industrial Average fell about 12 percent that day. The crash did not by itself cause every feature of the Great Depression, but it became its most famous financial symbol and helped deepen economic distress.
A common mix-up is treating Black Tuesday as the beginning of the entire crash. The severe decline unfolded over several trading sessions, and the market continued falling after October 1929, reaching its low in July 1932.