Which 1987 crash led U.S. exchanges to introduce market-wide circuit breakers?

Black Monday led U.S. exchanges to introduce market-wide circuit breakers after the 1987 crash.

On October 19, 1987, the Dow Jones Industrial Average lost 22.6% in one session. The scale and speed of the fall raised concerns that automated and program trading could intensify a panic before investors had time to assess information. Regulators and exchanges therefore examined ways to interrupt trading during extreme market movements.

The resulting circuit breakers, also called trading curbs, were intended to provide a temporary pause rather than permanently stop markets. They were first implemented in the late 1980s and have been revised several times. The details have changed, including the thresholds and lengths of trading halts.

Black Monday is sometimes confused with Black Tuesday, the 1929 crash date, or with later market declines using similar color-based names. The important connection here is institutional: the 1987 collapse directly influenced the modern use of automatic pauses in U.S. equity trading.