U.S. unemployment peaked at approximately 25 percent during the Great Depression.
The peak is generally associated with 1933, when about one-quarter of the U.S. labor force was unemployed. Industrial production, investment, banking activity, and international trade had all fallen dramatically after the financial crisis and economic contraction that began in 1929.
The estimate concerns the labor force, not the entire population. It also does not fully capture underemployment, reduced hours, discouraged workers, or people relying on irregular relief work, so the social impact was broader than the headline percentage suggests.
Unemployment declined during the 1930s as recovery policies, financial reforms, and later wartime mobilization changed economic conditions. The Great Depression was international, but unemployment rates differed substantially between countries.