The 1929 U.S. stock-market crash day when the Dow fell nearly 13% on October 28 was Black Monday.
The market had already suffered a major shock on Black Thursday, October 24, 1929. After a brief recovery attempt, selling accelerated on October 28, when the Dow Jones Industrial Average lost 38.33 points, or about 12.8%.
The following day, October 29, became known as Black Tuesday. The Dow dropped another 11.7%, and the combined losses destroyed much of the speculative value built during the 1920s.
The crash did not by itself cause every feature of the Great Depression. Bank failures, reduced demand, debt, policy decisions, and international economic problems deepened the downturn. The Dow eventually reached a low in July 1932, far below its 1929 peak.