March 9, 2020, was the first U.S. stock-market trading day in the COVID-19 crash to trigger market-wide circuit breakers.
The S&P 500 fell more than 7% shortly after trading began, activating a Level 1 halt that paused trading for 15 minutes. The sell-off reflected growing concern about the coronavirus pandemic, economic shutdowns, and an oil-price shock.
Additional U.S. circuit-breaker halts occurred on March 12, March 16, and March 18. The mechanisms had been created after earlier crashes to give investors time to absorb information and reduce disorderly selling.
March 9 is often confused with March 16, which produced another major decline, or March 23, when the S&P 500 reached its closing low for the crash. These dates mark different stages of the same market episode.