La Follette Jr. was born in Madison, Wisconsin. He attended the University of Wisconsin–Madison, where he was a member of Phi Beta Kappa and served as the editor of the student newspaper, The Daily Cardinal. He graduated in 1917 and served in the United States Army during World War I.
After the war, La Follette Jr. returned to Wisconsin and began his law practice. He also became active in politics, and in 1922 he was elected to the Wisconsin State Senate. He served one term in the Senate, and in 1925 he was elected to the United States Senate.
La Follette Jr. was a leading progressive during his time in the Senate. He supported public ownership of utilities, social welfare programs, and labor unions. He was also a strong opponent of isolationism and was one of the few senators to vote against the Neutrality Acts of the 1930s.
In 1946, La Follette Jr. was re-elected to the Senate by a wide margin. He died in office in 1953. He is considered one of the most influential progressive senators of the 20th century.
In addition to his political career, La Follette Jr. was also a prolific author and journalist. He wrote several books, including "La Follette's Autobiography" (1913) and "The Making of America" (1928). He also wrote articles for magazines such as The Nation, The New Republic, and Harper's Magazine.