A circuit breaker halted U.S. stock trading during the March 2020 market crash.
On March 9, 2020, trading in U.S. equities was halted after the S&P 500 fell 7% from its previous close. The pause was triggered by a Level 1 market-wide circuit breaker, designed to give investors time to absorb extraordinary price movements and reduce disorderly selling.
Similar halts occurred on March 12, March 16, and March 18 as the COVID-19 pandemic caused unprecedented uncertainty about public health, economic activity, and energy markets. The S&P 500 ultimately entered a bear market in March after reaching a record high in February.
A circuit breaker is a market mechanism, not a company-specific trading suspension and not a bank holiday. U.S. rules use threshold levels based on the S&P 500: trading pauses at declines of 7% and 13%, while a 20% fall triggers a halt for the rest of the session.