The 29 October 1929 Wall Street crash is known as Black Tuesday.
Black Tuesday followed Black Thursday, 24 October, and another severe selling session on Monday, 28 October. On 29 October, about 16 million shares changed hands on the New York Stock Exchange, then an exceptionally large volume. The Dow Jones Industrial Average fell about 12.8% that day.
The crash did not single-handedly cause the Great Depression. Economic contraction, bank failures, falling production, debt, and policy decisions all contributed to the prolonged downturn. However, the 1929 collapse became its most famous financial symbol.
A common mix-up is treating Black Tuesday as the entire crash. The Wall Street collapse unfolded across several days and was preceded by a major rise in share prices during the 1920s. The Dow eventually fell almost 89% from its September 1929 peak to its July 1932 low.