Which date is known as Black Monday, the worst single-day percentage fall in Dow Jones history?

Black Monday, the worst single-day percentage fall in Dow Jones history, occurred on October 19, 1987.

The Dow Jones Industrial Average fell 508 points, or 22.6%, in one trading session. Stock markets in other countries also plunged, making the event a genuinely global crash rather than an isolated American decline.

Several factors contributed, including rising interest rates, concerns about the U.S. trade deficit, computerized trading strategies, and portfolio-insurance programs that encouraged selling as prices fell. The exact causes remain debated, but the scale of the fall made market regulators reconsider trading safeguards.

Black Monday is often confused with the 1929 Wall Street Crash because both involved dramatic October declines. Unlike 1929, the 1987 crash was followed by a relatively quick recovery, and the U.S. economy did not enter a depression.