What date was Black Monday, the 1987 stock-market crash’s biggest one-day fall?

Black Monday, the 1987 stock-market crash’s biggest one-day fall, occurred on October 19, 1987.

The Dow Jones Industrial Average fell 508 points that day, a decline of 22.6 percent. In percentage terms, it remains the largest one-day percentage loss in the Dow’s history. Stock markets in other countries also suffered steep declines, making the event an international financial shock rather than only a U.S. episode.

Several factors contributed. Valuations were high, interest rates had risen, and computerized trading programs could automatically sell when prices moved lower. Portfolio-insurance strategies intensified the rush of sell orders. The exact balance among these causes remains debated, but the scale of the selling was unmistakable.

Black Monday is often confused with Black Tuesday in 1929. The names refer to different crashes separated by nearly six decades. After 1987, regulators introduced or strengthened safeguards such as circuit breakers to pause trading during exceptionally rapid declines.