The October 19, 1987 stock-market crash is known as Black Monday.
On that day, the Dow Jones Industrial Average fell 508 points, or 22.6 percent. It remains the largest one-day percentage decline in the Dow’s history. Major markets around the world also suffered steep losses, making the event an international crash rather than an isolated American sell-off.
Several forces contributed, including investor anxiety about interest rates, trade deficits, overvalued shares, and computerized trading strategies such as portfolio insurance. Those systems could generate large sell orders as prices dropped, intensifying the decline.
Black Monday is sometimes confused with Black Tuesday in 1929, but the two crashes occurred nearly six decades apart. Unlike the 1929 crash, the 1987 collapse did not lead to a prolonged economic depression.