On what date did the first major sell-off of the 1929 Wall Street Crash occur?

The first major sell-off of the 1929 Wall Street Crash occurred on October 24, 1929.

October 24 became known as Black Thursday. Heavy selling on the New York Stock Exchange overwhelmed buyers, and the Dow Jones Industrial Average fell sharply. A group of leading bankers later attempted to restore confidence by buying selected shares, temporarily calming the market.

The relief did not last. Selling intensified on October 28, known as Black Monday, and again on October 29, known as Black Tuesday. Those later sessions became more closely associated with the crash in popular memory, but October 24 marked the first major break after the market’s long rise.

The crash followed years of speculative buying, widespread use of margin, and strong optimism about stock prices. It did not by itself cause the entire Great Depression, although it deepened financial distress and damaged confidence.