Born in Wallace, South Dakota, Humphrey attended the University of Minnesota. In 1943, he became a professor of political science at Macalester College and ran a failed campaign for mayor of Minneapolis. He helped found the Minnesota Democratic–Farmer–Labor Party (DFL) in 1944; the next year he was elected mayor of Minneapolis, serving until 1948 and co-founding the liberal anti-communist group Americans for Democratic Action in 1947. In 1948, he was elected to the U.S. Senate and successfully advocated for the inclusion of a proposal to end racial segregation in the 1948 Democratic National Convention's party platform. He was a leader of American liberalism, especially in supporting civil rights. Liberals split over his strong support for the Vietnam War.