The first U.S. S&P 500 circuit breaker triggered during the COVID-19 market crash on March 9, 2020.
The S&P 500 fell 7% shortly after trading began, activating a Level 1 market-wide trading halt. It was the first such halt since the circuit-breaker system was revised after the 2010 Flash Crash. Trading paused for 15 minutes before resuming.
The plunge followed escalating concerns about the coronavirus pandemic, an oil-price dispute between Saudi Arabia and Russia, and rapidly worsening expectations for global economic activity. Markets then experienced further severe sessions, including additional circuit-breaker activations on March 12 and March 16.
A circuit breaker is a temporary pause, not a permanent closure of the market. The 2020 rules use percentage thresholds tied to the S&P 500, so the halt is different from an ordinary drop measured only in points. The New York Stock Exchange and Nasdaq both operate under the U.S. market-wide framework.