U.S. stock-market circuit breakers first activated during the COVID-19 market crash on March 9, 2020.
The S&P 500 fell 7% shortly after trading began, triggering a Level 1 market-wide circuit breaker and a 15-minute trading halt. The sharp decline reflected spreading concern about COVID-19, economic disruption, and a sudden oil-price shock after an agreement among major producers broke down.
Trading halts also occurred on March 12, March 16, and March 18, 2020, as markets continued to experience extreme volatility. These mechanisms are designed to pause trading after large index declines, giving participants time to assess information and reducing the risk of disorderly selling.
The March 9 halt was the first activation since the circuit-breaker system was revised after the 2010 Flash Crash. It was not the only major market shock during the pandemic: the S&P 500 reached its crash low on March 23 before beginning a powerful recovery.