Which U.S. stock exchange introduced the first circuit breaker after the 1987 Black Monday crash?

The New York Stock Exchange introduced the first modern stock-market circuit breakers after the 1987 Black Monday crash.

The October 19, 1987, collapse exposed how rapidly computerized trading and synchronized selling could overwhelm market liquidity. In response, U.S. regulators and exchanges developed rules that temporarily halt trading when broad market declines reach specified thresholds.

The NYSE's system was designed to give investors and market makers time to absorb information and restore orderly trading. Circuit breakers do not prevent prices from falling, and they cannot guarantee that trading will resume at a higher level. Their purpose is to interrupt extreme speed and reduce the risk of a disorderly cascade.

Modern U.S. rules use S&P 500 percentage declines for market-wide Level 1, Level 2, and Level 3 halts. These rules differ from single-stock limit-up-limit-down mechanisms. The NYSE is therefore the correct exchange in the historical question, even though modern circuit-breaker rules apply across U.S. markets.