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

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

The Dow Jones Industrial Average fell 508 points, or 22.6%, in a single trading session. The percentage decline remains the index's largest one-day loss, even though later crashes produced larger point losses because the index had grown substantially.

The fall spread rapidly through international markets. Hong Kong declined first, and European and American markets followed. Analysts associated the crash with overvalued shares, rising interest rates, market anxiety, and computerized portfolio insurance. The exact combination of causes remains debated.

The crash led regulators and exchanges to strengthen circuit breakers. These temporary trading halts are designed to slow panic and give investors time to assess rapidly changing prices. Black Monday is often confused with the October 1929 crash, but the 1987 event was much more severe in one-day percentage terms.