On what date did the 1987 stock-market crash reach its largest one-day Dow decline?

The 1987 stock-market crash reached its largest one-day Dow decline on October 19, 1987.

Known as Black Monday, October 19 saw the Dow Jones Industrial Average fall 508 points, or 22.6 percent. It remains the largest single-day percentage decline in the Dow’s history. Selling spread through international markets, making the event a genuinely global crash rather than an isolated New York episode.

Several factors were discussed afterward, including rising interest rates, trade tensions, overvalued shares, portfolio insurance, and computerized trading strategies. No single explanation fully accounts for the speed and scale of the decline.

The 1987 crash differed from 1929 in an important way: the market recovered relatively quickly, and the crash did not lead to a depression on the scale of the 1930s. Regulators later introduced circuit breakers and other safeguards designed to slow disorderly trading.