From 1960, Mayall spent 11 years as director of the Kitt Peak National Observatory until his retirement in 1971. Under his leadership KPNO, and the Cerro Tololo Inter-American Observatory, developed into two of the world's top research observatories, equipped with premier telescopes. Mayall was responsible for the construction of the Kitt Peak reflector, which was named after him. When Mayall died in 1993, his ashes were spread high on an empty ridge of Kitt Peak.