October 19, 1987, is known as Black Monday, when the Dow suffered its largest one-day percentage drop.
The Dow Jones Industrial Average fell 22.6% on that day, the largest single-day percentage decline in its history. Stock markets around the world also plunged, making the event a global crash rather than a problem confined to the United States.
Several factors contributed to the panic. Investors were concerned about overvalued shares, trade tensions, rising interest rates, and a widening U.S. trade deficit. Computerized trading strategies and portfolio insurance also accelerated selling once prices began to fall.
Unlike the 1929 crash, Black Monday did not lead to a decade-long depression. Central banks supplied liquidity, and regulators later introduced circuit breakers designed to pause trading during exceptionally sharp movements. The crash remains a major example of how modern market technology can amplify fear as well as improve speed and efficiency.