Intrigued with New Deal politics, he switched careers. Gruening was appointed to the U.S. delegation to the 7th Inter-American Conference in 1933, Director of the Division of Territories and Island Possessions of the Department of the Interior, 1934–1939, and Administrator of the Puerto Rico Reconstruction Administration, 1935–1937. He was a member of the Alaska International Highway Commission from 1938 to 1942. In 1939, Gruening was appointed Governor of the Territory of Alaska, and served in that position for 13 1/2 years. He was a delegate to the Democratic National Conventions of 1952, 1956, and 1960, and was elected to the United States Senate in 1958, serving for 10 years.