Born in Belleville, Illinois on July 7, 1927, he attended Illinois public schools and later earned his bachelor's degree from the University of Illinois at Urbana-Champaign and his JD from Washington University. During World War II, Dixon served in the United States Navy. Dixon served as a member of the Illinois House of Representatives from 1951-1963 and as a member of the Illinois State Senate from 1963-1971, serving as minority whip for part of that time. In 1970 he was elected Illinois Treasurer, an office he kept until 1977. In 1976 he was elected Illinois Secretary of State and served in that position until 1981 when he took office as a United States Senator from Illinois. In 1992 he lost in the Democratic Primary for U.S. Senate to Carol Moseley-Braun; his vote to confirm Clarence Thomas to the Supreme Court may have contributed to his defeat.

Dixon chaired the Defense Base Closure and Realignment Commission in 1994 and 1995. Dixon has since resumed practicing law with the Bryan Cave law firm in St. Louis and now lives in Fairview, Illinois.