October 29, 1929, was known as Black Tuesday during the Wall Street Crash.
On that day, about 16 million shares changed hands on the New York Stock Exchange, a record at the time. The Dow Jones Industrial Average fell roughly 12%, following a 13% decline on Black Monday, October 28.
Black Tuesday did not begin the crash by itself. Prices had already fallen from their September peak, and heavy selling had also occurred on Black Thursday, October 24. However, the October 29 collapse became the best-known symbol of the crash.
The crash helped usher in the Great Depression, although historians generally describe the depression as having multiple causes, including banking failures, debt problems, falling demand, and weaknesses in the international economy.