The 1987 stock-market crash became known as Black Monday.
On October 19, 1987, the Dow Jones Industrial Average dropped 508 points, or 22.6%, its largest one-day percentage decline in its history. Major markets in Hong Kong, Europe, Australia, and elsewhere also fell sharply, making the event global rather than exclusively American.
Several factors contributed, including high valuations, rising interest rates, trade concerns, and automated portfolio-insurance strategies. Those computer-based trading systems could intensify selling once prices began to fall. The precise cause remains debated, but the scale of synchronized declines is undisputed.
Black Monday did not lead to a prolonged depression like the 1929 crash. The U.S. economy continued expanding, and the Dow eventually recovered. Regulators later introduced circuit breakers and other safeguards designed to pause trading during exceptionally rapid market declines.