Soon after leaving college, starting work for a New York law firm, and marrying, Franklin D. Roosevelt decided on a career in politics. His first opportunity came in 1910, when he was elected to the state senate. His leadership of upstate New York Democrats in a fight against Tammany Hall enhanced his stature nationally. In 1912, after strongly backing Woodrow Wilson through intra-party struggles, Roosevelt was named assistant secretary of the navy.

In 1920, he won the Democratic nomination for vice president, with the ticket losing to Harding's campaign. The following year, while vacationing at his summer home in Canada, he was stricken with polio. Rather than retire and live off family wealth, he regained both his strength and desire for public office. His first stop was the governorship of New York in 1928. Major measures instituted during his term included public power, civil service reform, and social welfare. He was re-elected in 1930, setting the stage for a run a the presidency. Roosevelt won the 1932 Democratic presidential nomination. At the convention, where he overcame claims that he was not fit intellectually or physically for the position, he announced his plans for a New Deal.

He won the election and near his March 1933 inauguration the nation's banking system collapsed. Millions of depositors tried to withdraw savings and more than 12 million Americans were out of work. That was the base for his statement, "the only thing we have to fear is fear itself." That same day he closed the banks, summoned a special session of Congress, and began the process leading to emergency banking legislation that allowed the banks to reopen. The Roosevelt New Deal encompassed a massive social reorganization. The major pieces included the Agricultural Adjustment Administration to develop recovery in that realm, National Recovery Administration, social security, Farm Credit Administration, Works Progress Administration (WPA), and the Tennessee Valley Authority. While he hoped to expand his efforts beyond even those, he was hindered by charges of socialism and the declining popularity of the New Deal in the late 1930's.

Roosevelt hoped to keep the United States out of World War II. Adolf Hitler's military victories in Europe, culminating in the fall of France in 1940, prompted Roosevelt's decision to run for a third term. The Japanese attack on Pearl Harbor and Germany's declaration of war gave a new sense of mission. Roosevelt and Winston Churchill had agreed on an Atlantic Charter, an idealistic statement of peace-time aims, prior to the Japanese attack, and Roosevelt insisted on limiting Allied efforts to military victory. Among his other personal interests, Franklin Roosevelt was the nation's best -known stamp collector.