What was the nickname of the 1929 U.S. stock-market collapse's first major trading day?

The first major trading day of the 1929 U.S. stock-market collapse was nicknamed Black Thursday.

Black Thursday was October 24, 1929, when heavy selling on the New York Stock Exchange drove prices sharply lower. Banking interests temporarily tried to stabilize leading shares, but confidence remained fragile and the market soon experienced additional devastating sessions.

Black Monday followed on October 28, and Black Tuesday came on October 29. Black Tuesday is often treated as the most famous day of the crash, but Black Thursday began the sequence of panic selling that destroyed much of the market's value.

The crash did not by itself create every hardship of the Great Depression. Falling investment, bank failures, reduced lending, unemployment, and international economic problems interacted over several years. The crash nevertheless became its defining financial symbol.