What was the name of the 24 October 1929 sell-off during the Wall Street Crash?

The 24 October 1929 sell-off during the Wall Street Crash was called Black Thursday.

Heavy selling struck the New York Stock Exchange after weeks of uncertainty. The Dow Jones Industrial Average opened sharply lower, and trading volume reached a then-record level. A group of major bankers later bought selected shares to calm the market, and the Dow recovered much of its early loss by the close.

The intervention did not end the crisis. Selling returned with greater force on 28 October, known as Black Monday, and on 29 October, known as Black Tuesday. Those sessions helped destroy confidence in the late-1920s stock boom.

Black Thursday is therefore an important early stage of the crash, not the single day on which the entire decline occurred. The market’s long descent continued into 1932.