The Business Cycle Dating Committee of the National Bureau of Economic Research has a very important job. It is responsible for determining the peaks and troughs of business cycles in the United States. It thus decides how long recessions are and also how long expansions are. The Chair of the Committee is Professor Robert Hall of Stanford University.
The latest decision of Committee occurred just this week on July 19, 2021. The Committee decided that a trough in monthly economic activity occurred back in April 2020. They also determined that the previous peak occurred back in February 2020. Thus the recession, measured by the decline in employment from peak to trough, lasted only two months. It was the shortest recession in United States history. It was completely caused by COVID-19.
This chart shows total employment in the United States. You can see that the peak in employment occurred in February and the trough occurred in April. Though only lasting two months the decline in employment was huge at 25.4 million.