During the 1987 global stock-market crash, October 19's record one-day collapse was called Black Monday.
On that Monday, the Dow Jones Industrial Average fell 508 points, or 22.6 percent, then the largest one-day percentage decline in its history. Stock markets in other countries also dropped sharply, making the event international rather than solely American.
Several factors contributed, including computerized program trading, portfolio insurance, high valuations, and concerns about interest rates and trade deficits. The exact combination intensified selling, but no single event fully explains the crash.
Black Monday is sometimes confused with the 1929 Wall Street Crash, whose most famous dates include Black Tuesday. The 1987 crash did not produce a depression, and new market safeguards, including circuit breakers, were later introduced to slow extreme declines.