October 19, 1987, was nicknamed Black Monday, the day global stock markets suffered their largest one-day percentage falls.
The Dow Jones Industrial Average dropped 508 points, or 22.6 percent, in a single session. That percentage decline was greater than the one-day fall on any day of the 1929 crash. Markets in Hong Kong, London, Australia, and several other financial centers also plunged, making the event international rather than purely American.
Several factors were blamed, including rising interest rates, investor anxiety, portfolio insurance, and program trading. The exact combination remains debated, but automated selling helped accelerate the decline once prices began falling.
Despite the dramatic collapse, the 1987 crash did not produce a depression comparable to the 1930s. Central banks supplied liquidity, financial institutions remained operating, and markets eventually recovered. The episode nevertheless influenced later trading safeguards and circuit breakers.