The Ent Air Force Base was an Air Force base located in the Knob Hill neighborhood of Colorado Springs, Colorado. A tent city, established in 1943 to build the base, was initially commanded by Major General Uzal Girard Ent (1900-1948) for whom the base is named. The base was opened in 1951. From 1957 to 1963, the base was the site of North American Aerospace Defense Command (NORAD), which moved to the Cheyenne Mountain Air Force Station. The base became the Ent Annex to the Cheyenne Mountain facility in 1975. The facility was closed in 1976 (becoming a Formerly Used Defense Sites).