[1][2][3] As a child, Gill lived in several southern U.S. cities, including Atlanta, Georgia, where he graduated from Bass High School in 1954.

He entered the U.S. Air Force as a second lieutenant, and also attended a special graduate meteorology program at the University of Chicago in 1958 and 1959.

In 1967 he enrolled as a graduate student at Colorado State University, and received his PhD in classical complex analysis in 1971.

By the mid-1950s he had begun to specialize in very short, acrobatic routes on outcrops and boulders, establishing problems in the 1950s and early 1960s considerably harder than those existing at the time.

According to Alpinist magazine, "His introduction of chalk and dynamic movement marked the beginning of modern climbing in America.

In the Tetons, in 1958, John Gill climbed a short route on Baxter's Pinnacle that lies in the 5.10 realm, before that grade was formally recognized — one of the first to be done in America.

In the 1950s, John Gill introduced a very early – if not the first – grading system specifically designed for bouldering and not restricted to a particular area.

The introduction of sport climbing some twenty years later and more intense competition weakened the philosophical underpinnings of the three-tiered structure, although climbers such as Jim Holloway adopted personal three-level systems similar to Gill's.

[20] He accomplished a number of difficult stunts on the rings, including inverted and olympic crosses, giant swings, and slow pulls from hang to handstand.