The S&P 500 fell about 34% between February 19 and March 23, 2020, during the 2020 stock-market crash.
Investors reacted to the global spread of COVID-19, business closures, travel restrictions, supply disruptions, and uncertainty about future earnings. The S&P 500 reached a record closing high of 3,386.15 on February 19, 2020, then entered a bear market in March.
Trading was halted several times under market circuit breakers as prices fell rapidly. The index reached its closing low for the initial crash on March 23 at 2,237.40. Extraordinary monetary and fiscal support, combined with changing expectations about the pandemic, helped markets recover later in 2020.
The crash affected multiple indexes and countries, so the S&P 500 is not the only valid measure of the episode. It is a particularly useful benchmark because it represents 500 large U.S. companies and is widely followed internationally.