Black Monday, the 1987 stock-market crash's record one-day percentage fall in the Dow Jones Industrial Average, occurred on 19 October 1987.
The Dow Jones Industrial Average fell 508 points, or 22.6%, that day. The percentage decline remains the largest single-day fall in the index's history. Stock markets in other countries also suffered severe losses, making the event a worldwide crash rather than an isolated American sell-off.
Several factors contributed. Valuations were high, investors were worried about interest rates and trade imbalances, and computerized portfolio-insurance strategies automatically sold futures as prices declined. Those programmed sales added pressure to an already nervous market.
Black Monday is often confused with the 1929 crash because both happened in October. The dates are different: 1987's Black Monday was 19 October, while the most famous 1929 crash days were Black Thursday and Black Tuesday. The Dow later recovered, and regulators introduced safeguards such as trading halts.