The severe Wall Street decline on October 28, 1929, was called Black Monday.
The Dow Jones Industrial Average dropped approximately 12.8% that day, one of the largest percentage losses in its history at the time. The decline came after renewed selling pressure and helped create the panic that continued into October 29, later remembered as Black Tuesday. Together, these sessions made the 1929 crash especially dramatic in the public memory.
The labels are chronological, not interchangeable. Black Thursday refers to October 24, when unusually heavy selling initially alarmed investors. Black Monday refers to October 28, and Black Tuesday refers to October 29. These names describe trading days rather than separate economic crises.
The crash developed after a prolonged speculative boom in U.S. shares. Many investors had bought stocks with borrowed money, so falling prices forced margin calls and additional selling. Although the crash was a major financial shock, the broader Depression also involved banking problems, policy choices, debt, and collapsing demand.