Black Monday was the nickname of October 28, 1929, the U.S. market day that followed Black Thursday.
The Wall Street Crash of 1929 unfolded across several dramatic sessions. On Thursday, October 24, heavy selling was partly contained by support from major bankers. Selling returned with greater force on Monday, October 28, when the Dow Jones Industrial Average fell 12.8 percent. The following day, October 29, became Black Tuesday and brought another devastating decline.
The crash damaged confidence and helped deepen the economic contraction that became the Great Depression. It did not single-handedly cause every feature of the Depression: bank failures, falling demand, monetary policy and international debt problems also mattered.
Black Monday is distinct from the 1987 Black Monday, when U.S. share prices suffered their famous one-day percentage collapse. The 1929 label refers specifically to October 28, 1929.