As a graduate student in geology at Rice University, McKay was present at John F. Kennedy's speech in 1962 announcing the goal of landing a man on the Moon within the decade. Inspired by Kennedy's speech, McKay as a NASA scientist trained the Apollo astronauts in geology. He was a chief trainer for Neil Armstrong and Buzz Aldrin during their last geology field trip in West Texas. On July 20, 1969 in Houston McKay was the only geologist present in the Apollo Mission Control Room when Armstrong and Aldrin walked on the Moon, serving as a resource. He was named principal investigator to study the samples which they brought back from the Moon.