What was the fastest bear market in US stock-market history, beginning during the COVID-19 pandemic in 2020?

The 2020 stock-market crash was the fastest bear market in US stock-market history.

US and global equities fell sharply in February and March 2020 as the COVID-19 pandemic spread. Governments introduced lockdowns and travel restrictions, businesses closed, and investors feared a severe global recession. The S&P 500 entered a bear market on March 12 and reached its initial pandemic-era low on March 23.

The Federal Reserve cut interest rates, expanded asset purchases, and introduced emergency lending facilities. Governments also announced large fiscal-support programs. These measures, together with changing expectations about vaccines and reopening, helped markets recover rapidly from the March low.

The crash differed from many earlier crises because its immediate trigger was a public-health emergency rather than a banking collapse. Nevertheless, market volatility was amplified by the economic shock, uncertainty, and forced selling in some financial markets.