What was the nickname of the 24 October 1929 New York Stock Exchange crash day?

The 24 October 1929 New York Stock Exchange crash day was known as Black Thursday.

Heavy selling overwhelmed the exchange that morning, and the Dow Jones Industrial Average fell sharply. A group of leading bankers later attempted to restore confidence by buying major stocks, temporarily stabilizing prices. The relief did not last: further panic selling occurred on Black Monday and Black Tuesday the following week.

Black Thursday is therefore an opening landmark of the Wall Street Crash, not the final or largest single day of the episode. The market had already shown weakness after reaching a peak in September 1929, while speculation funded by borrowed money left many investors vulnerable to margin calls.

The crash contributed to a much broader economic breakdown. It is inaccurate to say that one trading day alone created the Great Depression; banking failures, deflation, falling demand, and policy decisions all helped turn the market collapse into a prolonged worldwide crisis.