October 19, 1987, marked the biggest one-day percentage fall in Dow Jones history during the 1987 stock market crash.
That Monday became known as Black Monday after the Dow Jones Industrial Average fell 22.6% in a single trading session. The drop exceeded the losses recorded on the most dramatic days of the 1929 crash and remains the index’s largest one-day percentage decline.
Several forces contributed, including rising interest rates, anxiety about trade deficits, a declining dollar, and program trading strategies that automatically sold securities as prices fell. Selling spread rapidly between markets in the United States, Europe, and Asia, showing how increasingly connected global finance had become.
The crash did not develop into a prolonged depression like the 1930s crisis. The Federal Reserve, led by Alan Greenspan, supplied reassurance and liquidity, while markets gradually stabilized. The episode also encouraged exchanges to develop circuit breakers designed to pause trading during extreme declines.