The Wall Street stock-market collapse on Tuesday, October 29, 1929, is known as Black Tuesday.
On that day, investors traded roughly 16 million shares on the New York Stock Exchange, then an extraordinary volume. The Dow Jones Industrial Average fell about 12%, following a major decline on Black Monday, October 28.
Black Tuesday did not single-handedly cause the Great Depression. The crash exposed excessive speculation and margin buying, while bank failures, shrinking investment, falling production, and international economic problems deepened the downturn.
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 both dates and did not reach its bear-market low until July 1932.