The Dow Jones Industrial Average lost 508 points on October 19, 1987, during Black Monday.
The drop carried the Dow from 2,246.74 to 1,738.74, a fall of 22.6% in a single session. It remains the largest one-day percentage decline in the index’s history, although later market levels made the raw point total look less dramatic by comparison.
The crash was global: markets in Hong Kong, London, Australia, Canada, and several other financial centers also fell sharply. Program trading, portfolio insurance, international market connections, and investor panic all contributed to the speed of the decline.
The crash did not produce a prolonged economic depression like the 1929 collapse. The U.S. Federal Reserve, led by Alan Greenspan, issued a statement affirming its readiness to provide liquidity to the financial system.