October 29, 1929, is known as Black Tuesday, the day U.S. share prices suffered a historic collapse.
The Dow Jones Industrial Average fell 12.8% on Black Tuesday, after dropping 11.7% on Black Monday, October 28. Heavy selling overwhelmed the New York Stock Exchange, with roughly 16 million shares changing hands, then an extraordinary volume for the period.
Black Tuesday did not by itself cause the entire Great Depression. The crash followed years of speculative buying, widespread purchases on margin, weakening economic conditions, and declining industrial profits. The banking failures and contraction that followed deepened the crisis.
A common mix-up is calling October 24, 1929, Black Tuesday. October 24 was Black Thursday; October 29 was Black Tuesday. The Dow continued falling after 1929 and did not reach its bear-market low until July 1932.