24 October 1929, the first major Wall Street sell-off of the 1929 crash, is known as Black Thursday.
The day saw exceptionally heavy trading on the New York Stock Exchange, with roughly 12.9 million shares changing hands. Prices fell sharply at the opening, and the decline spread fear among investors. A group of prominent bankers later bought shares to support prices, producing a temporary recovery.
The panic did not end on Black Thursday. Selling intensified on 28 October, called Black Monday, and reached another dramatic low on 29 October, called Black Tuesday. The crash unfolded alongside a broader economic downturn that became the Great Depression, although historians identify multiple causes rather than one single event.
Black Thursday refers specifically to 24 October, not to the crash’s overall duration. The New York market eventually reached a much lower bottom in July 1932.