October 19, 1987, was known as Black Monday, the day of a historic global stock-market collapse.
The Dow Jones Industrial Average fell 508 points, or 22.61%, in a single trading session. That percentage decline remains the largest one-day fall in the Dow’s history. Markets in Hong Kong, London, Australia, and many other financial centers also plunged, showing how quickly modern electronic trading could transmit panic across borders.
Several explanations have been proposed, including overvalued shares, rising interest rates, trade tensions, portfolio insurance, and computerized selling strategies. No single cause completely explains the speed and scale of the fall. Unlike the crash of 1929, Black Monday was not followed by a decade-long depression in the United States.
The Federal Reserve, led by Alan Greenspan, issued a statement affirming its readiness to provide liquidity to the financial system. Trading rules were later revised, including the development of circuit breakers designed to pause markets during extreme declines. “Black Monday” can refer to other crashes, but October 19, 1987, is its most famous financial use.