The trading day beginning on 24 October 1929 is known as Black Thursday in the United States.
Black Thursday marked the first dramatic collapse in the Wall Street Crash of 1929. Heavy selling overwhelmed the New York Stock Exchange, and the Dow Jones Industrial Average fell sharply. A group of major bankers bought large quantities of leading shares late in the session, temporarily calming the market and creating the impression that the crisis had been contained.
That relief did not last. Selling intensified on Black Monday, 28 October, and Black Tuesday, 29 October. The Dow eventually reached a low in July 1932, losing nearly 89% from its September 1929 peak. The crash was one part of the broader Great Depression, which also involved bank failures, deflation, unemployment, and collapsing international trade.
Black Thursday is sometimes confused with Black Tuesday because Tuesday produced the most famous final panic. They were separate days within the same extended crash.