October 24, 1929, was called Black Thursday, the first major panic day of the Wall Street Crash of 1929.
On that Thursday, trading volume surged and the Dow Jones Industrial Average fell sharply, although it later recovered much of the decline. The selling alarmed investors because the market had risen dramatically during the 1920s and many shares had been bought with borrowed money.
The panic intensified in the following days. October 28 became known as Black Monday, and October 29 became Black Tuesday, when the Dow suffered another severe fall. These dates are often grouped together as the Wall Street Crash rather than treated as separate crashes.
The 1929 collapse did not by itself cause every feature of the Great Depression, but it damaged confidence, reduced wealth, and contributed to a wider contraction in investment and spending. A common mix-up is calling October 24 Black Tuesday; Black Thursday came five days earlier.