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Franklin D. Roosevelt was the president under whom Cordell Hull served as U.S. Secretary of State. Hull held this position during Roosevelt's entire presidency, from 1933 to 1944, making him the longest-serving Secretary of State in U.S. history. Hull played a pivotal role in shaping U.S. foreign policy during this period, particularly in promoting the Good Neighbor Policy and laying the groundwork for international organizations like the United Nations.