Black Monday was the U.S. stock-market crash that began on October 19, 1987, when the Dow Jones Industrial Average fell 22.6% in one session. That was the largest one-day percentage decline in the Dow’s history, exceeding the worst daily losses recorded during the 1929 crash.
The decline was part of a worldwide market sell-off. Analysts have pointed to several contributing factors, including rising interest rates, concerns about trade deficits, and computerized portfolio-insurance trading that could accelerate selling. No single cause fully explains the event, and investigations rejected the idea that one isolated piece of news caused the entire collapse.
The crash did not develop into a depression like the crisis of the 1930s. The Federal Reserve, led by Alan Greenspan, signaled that it would provide liquidity to the financial system. Markets recovered over time, although the event permanently changed thinking about market risk, trading technology, and circuit breakers.