Black Monday in the 1929 Wall Street Crash was 28 October 1929, when the Dow fell about 13%.
The decline followed the panic of Black Thursday and a brief weekend pause. On Monday, selling intensified across the New York Stock Exchange, and the Dow suffered one of its largest percentage losses of the period.
The next day, 29 October, became known as Black Tuesday and brought another exceptionally severe fall. Together, the two sessions destroyed enormous market value and became the most remembered days of the crash.
Black Monday is sometimes overlooked because Black Tuesday is more famous. The dates are distinct: Black Monday was 28 October, while Black Tuesday was 29 October. The crash continued for years, with the Dow eventually falling roughly 89% from its September 1929 peak to its 1932 low.