The 1929 US stock-market collapse’s October 24 opening crash day is known as Black Thursday.
On October 24, 1929, panic selling produced exceptionally heavy trading on the New York Stock Exchange. Major bankers met and announced a pool intended to support leading shares, helping prices recover temporarily. The intervention did not end the broader collapse.
Selling intensified again on October 28, known as Black Monday, and October 29, known as Black Tuesday. The crash is closely associated with the Great Depression, although the Depression had multiple causes, including banking failures, falling demand, debt problems, and international economic weaknesses.
Black Thursday is therefore not the name for every day of the 1929 crash. It specifically identifies Thursday, October 24, while Black Tuesday refers to the even more famous collapse on October 29.