The 1987 stock-market crash that began with a record one-day percentage fall on October 19 was Black Monday.
On October 19, 1987, the Dow Jones Industrial Average fell 508 points, or 22.6%. That remains the largest one-day percentage decline in the Dow’s history. Markets in other countries also dropped sharply, making the event an international crash rather than a purely American shock.
Several factors contributed. Investors worried about high valuations, rising interest rates, trade tensions, and a widening U.S. trade deficit. Computerized portfolio-insurance strategies and other programmed trading systems also accelerated selling once prices began to fall.
Black Monday is sometimes confused with the 1929 crash days that also received weekday nicknames. The Federal Reserve responded by publicly emphasizing its willingness to provide liquidity, while exchanges later introduced circuit breakers designed to pause trading during extreme declines.