Western Reserve Academy. Williams College.
He graduaded from Williams College, Williamstown, Massachusetts, in 1940 and Western Reserve University School of Law, now Case Western Reserve University School of Law, Cleveland, Ohio in 1945. Dennison worked for American Field Service 1942 to 1943, and was a lawyer in private practice. He was special counsel for Warren, Ohio 1950-1951, and special assistant to the Ohio Attorney General 1953-1956.
Dennison was elected as a Republican to the 85th United States Congress, (January 3, 1957 - January 3, 1959), and was unsuccessful for election to the 86th and 87th Congresses in 1958 and 1960.
Dennison was later a business executive and died in Warren, Ohio September 21, 2001.
After his service in Congress, Dennison was a consultant to the Civil Rights Commission in 1959, and a member of the Federal Trade Commission, 1970-1974.