Monday, October 19, 1987, is known as Black Monday because the Dow Jones Industrial Average fell 22.6% that day.
The decline was the largest one-day percentage fall in the Dow’s history. Selling spread rapidly through international markets: Hong Kong fell first, European markets followed, and Wall Street suffered its historic plunge. The crash came after a powerful multi-year rise in share prices.
Several explanations were discussed, including overvalued markets, trade and interest-rate concerns, portfolio insurance, and computerized trading strategies. No single cause fully explains the speed and scale of the worldwide sell-off. Trading systems and market rules were later reviewed extensively.
The crash did not produce a depression comparable to the 1930s. The Dow recovered much of its loss over the following months, although it did not regain its pre-crash closing level until 1989. Regulators also introduced circuit breakers designed to pause trading during extreme market moves.