The Dow Jones Industrial Average lost 12.8% at the close on Black Tuesday, October 29, 1929. That session was the final and most famous day of the Wall Street Crash’s initial sequence.
Black Tuesday followed Black Thursday on October 24 and Black Monday on October 28. Selling intensified as investors rushed to liquidate shares, while many stocks had previously been bought with borrowed money. Falling prices made it harder for investors to meet margin calls, which forced additional sales.
The crash did not by itself cause every feature of the Great Depression, but it severely damaged confidence and exposed weaknesses in the financial system. Banks, businesses, and households were affected by the subsequent contraction in credit and demand.
The 12.8% figure is a closing-to-closing percentage change for the Dow. It is different from the index’s larger cumulative decline over the following years and from the percentage loss recorded on Black Monday in 1987.