Term: 1933–1945
When Franklin D. Roosevelt took office in 1933, the United States was in the depths of the Great Depression. Roosevelt's response was the New Deal, a series of ambitious programs designed to provide relief, recovery, and reform. This deficit spending was a deliberate economic strategy based on the ideas of economist John Maynard Keynes, who argued that government intervention was necessary to stimulate a depressed economy.
While the New Deal increased the debt, it was World War II that caused it to skyrocket. Following the attack on Pearl Harbor in 1941, the U.S. economy was fully mobilized for war. The cost was astronomical. The government financed the effort through a combination of increased taxes and the sale of war bonds. This led to the largest and most rapid accumulation of debt in U.S. history.
Debt at Start of Term (1933): ~$22.5 billion
Debt at End of Term (1945): ~$258.7 billion
Total Increase: ~$236.2 billion
Percentage Increase: ~1,048%
By the end of Roosevelt's presidency, the national debt was higher than the nation's GDP. This monumental debt financed the victory in World War II and laid the groundwork for the post-war economic boom.