March 9, 2020, was the first day of the 2020 stock-market crash when the S&P 500 hit its 7% circuit breaker.
The halt occurred as investors reacted to the rapidly spreading COVID-19 pandemic and the collapse of an oil-production agreement between OPEC and Russia. The S&P 500 fell 7% shortly after the opening bell, triggering a Level 1 circuit breaker and pausing trading for 15 minutes.
Further major down days followed on March 12 and March 16. By March 23, the S&P 500 had fallen about 34% from its February 19 record close. Governments and central banks then introduced extraordinary fiscal, monetary, and public-health measures, and markets began a rapid rebound.
The circuit breaker did not prevent the crash; it temporarily interrupted trading to slow panic and allow information to circulate. Similar safeguards had been developed after earlier episodes, especially the 1987 crash. The 2020 market collapse was unusually swift, but its recovery was also historically rapid.