John Blackmon played football for two years at Sylacauga High before graduating in 1973. He then graduated from Auburn University before starting his coaching career as an assistant football coach at Randolph County High School.

After one year at Randolph County he spent two years as an assistant football coach at Villa Rica High School in Georgia. Blackmon returned to Alabama and spent five years (1983-87) as an assistant football coach at Benjamin Russell High in Alexander City. In 1988, he was named the head football coach at Leroy High School in southwest Alabama.

In six seasons at Leroy his Bears finished a combined 51-21 with the last four teams winning region titles and making the playoffs. Blackmons 1993 edition of the Bears posted a 13-1 record.

Coach Blackmon took the head football coaching position at his alma mater in 1994. Sylacauga was 1-9 the year prior to his arrival and finished 0-10 in his first season.

His next five teams qualified for the playoffs and won four region titles. He spent a total of ten seasons at Sylacauga with a record of 63-48.

In 2004, Blackmon accepted the head football job at Jackson High School. He stayed for four seasons before retiring as a head football coach in Alabama.

His overall record stands at 132-92 in 20 years as a head football coach. His teams won eight area and region titles and qualified for the playoffs 11 times.