Born in New York City, Gruening pursued a career in journalism after graduating from Harvard Medical School. After working for various newspapers in New York and Boston, he served in various roles during the administration of President Franklin D. Roosevelt. He was appointed as Governor of Alaska in 1939 and became a prominent advocate of Alaska statehood.
Gruening became one of Alaska's inaugural pair of senators, along with Bob Bartlett, after Alaska gained statehood in 1959. Gruening was a prominent opponent of the Vietnam War, and with Oregon's Wayne Morse, was one of just two senators to vote against the Gulf of Tonkin Resolution which allowed the bombing of North Vietnam. In 1968, Mike Gravel defeated Gruening in the Democratic Senate primary, and Gruening's attempt to win re-election as an independent was unsuccessful.
