Blackman was born on July 7, 1918, in De Soto, Iowa. He played football at the University of Southern California, beginning in 1937. Blackman was named a captain of the freshmen team, but stopped playing after being stricken with polio. He was named an assistant coach at USC while still an undergraduate student.
Coaching career
After head coaching stints at the San Diego Naval Academy, Pasadena City College, and the University of Denver, Blackman was named head coach at Dartmouth College in 1955, where he was universally known among players and students alike as "The Bullet." In 16 seasons under Blackman, Dartmouth had a record of 104–37–3, including undefeated seasons in 1962, 1965, and 1970 while leading Dartmouth to their first conference title in 60 years in 1958. They would win it six more times in his tenure, including his final season in 1970. In his final season at Dartmouth, Blackman received the Walter Camp Coach of the Year Award.