The October 24, 1929 trading session that opened the Wall Street Crash was nicknamed Black Thursday.
On that Thursday, heavy selling drove prices sharply lower on the New York Stock Exchange. The Dow Jones Industrial Average fell 11% during the day, although a group of major bankers later attempted to stabilize prices by buying leading stocks.
The intervention briefly calmed the market, but confidence did not return permanently. Selling resumed the following week, producing Black Monday on October 28 and Black Tuesday on October 29. Those sessions are often remembered together as the climactic phase of the crash.
The crash did not single-handedly cause the Great Depression. It was one part of a wider economic breakdown involving falling demand, bank failures, debt, international financial strains, and deflation. The market collapse nevertheless became its most recognizable financial symbol.