The 1929 market crash term for the New York exchange’s 28 October collapse, one day before Black Tuesday, was Black Monday.
On 28 October 1929, the Dow Jones Industrial Average fell 12.82 percent. The drop followed earlier selling during the same month and reflected collapsing confidence in heavily valued US shares. It was followed on 29 October by Black Tuesday, when another exceptionally large decline occurred.
These named days are part of the Wall Street Crash of 1929, which developed over several weeks rather than during one isolated session. Margin buying had allowed investors to purchase shares with borrowed money, so falling prices forced additional sales and intensified the downward movement.
Black Monday is easily confused with Black Tuesday and Black Thursday. Black Thursday refers to 24 October, while Black Tuesday refers to 29 October. The separate 1987 Black Monday occurred on 19 October 1987 and was a different crash.