The 1930s were dominated by economic collapse, stagnation, and mass unemployment. This crisis enabled the Democrats to recapture the White House and embark upon a period of reform unsurpassed until the 1960s. Roosevelt's New Deal laid the foundations of a welfare system that was further consolidated during and after the Second World War. American involvement in World War II helped to secure victory in Europe and in Asia. American participation in the war led to economic recovery but also brought with it enormous demographic and social changes. Some of these changes continued after the war had ended, but further political reform was to be limited due to the impact of the Cold War and the effects of America's new role as the world's leading superpower in the atomic age.

The Historical Dictionary of the Roosevelt-Truman Era examines significant individuals, organizations, and events in American political, economic, social, and cultural history between 1933 and 1953. This was a period of enormous significance in the United States due to the impact of the Great Depression, World War II, and the onset of the Cold War. The presidencies of Franklin D. Roosevelt and Harry S. Truman witnessed the origins of the modern American welfare system and the rise of the United States as a world power, as well as its involvement in the confrontation with communism that dominated the latter half of the 20th century.