During the 1987 stock-market crash, the Dow Jones Industrial Average lost 22.6% on October 19, 1987.
The fall occurred on what became known as Black Monday, the largest one-day percentage decline in the Dow’s history. Selling spread through markets worldwide, with major declines in Hong Kong, London, Australia, and Canada as well as the United States.
Several forces contributed, including rising interest rates, fears about economic growth, and international currency tensions. Computerized trading strategies and portfolio insurance also accelerated selling once prices began to drop. The decline was not caused by a single company failure.
The crash led U.S. regulators and exchanges to develop circuit breakers, which temporarily halt trading after exceptionally large falls. The Dow eventually recovered, but the event remains a major example of how modern financial markets can transmit panic rapidly across borders.