U.S. stock-market circuit breakers activated four times during the March 2020 COVID-19 crash.
The S&P 500 triggered market-wide Level 1 halts on March 9, March 12, March 16, and March 18, 2020. Each halt followed a fall of at least 7% from the previous close and paused trading for 15 minutes under the rules then in force.
The crash reflected the rapidly spreading coronavirus pandemic, lockdowns, collapsing expectations for business activity, and a historic oil-price dispute between Saudi Arabia and Russia. Investors moved rapidly out of risky assets, producing extraordinary volatility across global markets.
The four halts were a visible reminder of safeguards introduced after earlier crashes, especially Black Monday in 1987. Circuit breakers do not prevent losses or guarantee a rebound; they are designed to give investors time to assess information and reduce the risk of disorderly selling.