The historical significance of Franklin Delano Roosevelt's four terms as president includes his leadership during the Great Depression and World War II. Roosevelt implemented the New Deal, a series of programs and policies designed to provide economic relief and recovery, transforming the role of the federal government in American life. His presidency marked the expansion of social safety nets and increased government intervention in the economy. Additionally, FDR's leadership in wartime solidified the US's position as a global superpower and laid the groundwork for the post-war world order, influencing international relations for decades.