What was the first trading day of the 1929 Wall Street crash, before Black Tuesday?

The first major trading day of the 1929 Wall Street crash was Black Thursday, October 24, 1929.

Heavy selling overwhelmed the New York Stock Exchange that morning, and the Dow Jones Industrial Average fell sharply. A group of leading bankers later pooled resources to support prices, producing a temporary recovery and helping calm the market for a few days.

That intervention did not resolve the deeper problems of excessive speculation, buying on margin, and weakening economic conditions. Selling returned the following week, culminating in Black Monday and Black Tuesday. Black Thursday is therefore the opening day commonly identified with the crash, while Black Tuesday marked its most famous later collapse.