Federal Building (Ent AFB)

The Federal Building of the Ent AFB Defense Area is a Formerly Used Defense Site for Cold War military computer systems at Knob Hill in Colorado Springs and adjacent to the US Olympic Training Center's BP service station (separated by the OTC's perimeter fence). The facility was constructed in an excavated embankment at a street corner of the Ent Air Force Base perimeter by 1962 during the city's NORAD expansion. (The expansion included the Space Defense Center operational in the base's P4 Annex in 1961, the off-base Chidlaw Building opening in 1963 and outside of the city, Cheyenne Mountain bunker buildings complete in 1965.) The Federal Building's use by the US government continued after most Ent AFB land had transferred to the Olympic Committee in 1977. As one of the Ent Annex's remaining government facilities controlled by Peterson AFB, the Federal Building's USAF custody transferred from Aerospace Defense Command first to Strategic Air Command in 1980 and then "Space Command" in 1982 (renamed Air Force Space Command in 1985.)

Operations
After a BMEWS display facility with "austere and economical construction with minimum equipment" was planned for September 1960 in an "annex to the COC building" (blockhouse) built in 1954, the Federal Building was built and used for tbd.

Ent's "Federal Building" remained a military computer facility and was shared with the United States Census Bureau for the 1990 United States Census—military units of the United States Army and other services later moved from the Federal Building to Peterson AFB building 2 which had recently opened. The building is within a 1999 aerial photograph of the OTC, and in 2013 the structure was unused with an empty front entrance, an interior light illuminated on the 2nd floor, and military notices prohibiting trespassing and parking.