Ent AFB Defense Area

The "Ent AFB Defense Area" is a Knob Hill, Colorado, area of Formerly Used Defense Sites in Colorado Springs designated after the Ent Annex (former Ent Air Force Base) closed in the 1970s. In addition to structures of the Air Force Base such as the Federal Building, separate military facilities of the Defense Area include the Chidlaw Building and nearby, 3 preceding prefabricated office buildings along Bijou Street. Initiated as a tent camp in an open area at an early 1900s medical complex with the "Beth-El Hospital", the military facilities such as the leased USAAF 2nd Air Force headquarters building were within the portion of the city that had been annexed by 1906. Until named Ent AFB, the area was designated in unit addresses as at "Colorado Springs", e.g., the "Headquarters Area, Colorado Springs" was being used by 1947 and included 2 squadrons (the 201 AAFBU was the headquarters squadron for the 15th Air Force HQ.) In the 1970s most of Ent AFB became the United States Olympic Training Center in Colorado Springs.

Early 1900s hospitals
William Jackson Palmer c. 1874 donated a tract of Knob Hill land for a medical school, and subsequently built were St. Francis Hospital and the 1890-1902 Bellevue/National Deaconess Sanitarium. Bethel Hospital opened in 1911 along East Boulder Street (Beth-El Hospital in 1913) on land donated by General William Palmer (cf. the earlier "Bethel Chapel" at Wahsatch & Las Animas ). In 1918 on the east side of Beth-El Hospital, a 1918 Contagion Hospital opened--later renamed: "Daniels Hall or Nurses Home".) In 1926 on the east side of Beth-El Hospital and Daniels Hall, the National Methodist Sanitorium (Streamline Moderne architecture) opened on 29 acre (Beth-El Hospital was renamed "Memorial Hospital" after the city purchased it in 1943.) (sold to University of Colorado in the 21st Century).  The sanitorium building became the Air Defense Command/NORAD headquarters during the Cold War.

Colorado Springs Tent Camp
The Colorado Springs Tent Camp was established in 1943, and by 15 July 1944, the "2nd Air Force"at "Colorado Springs" was under the command of "Brig. Gen. U. G. Ent". Post-war the Tent Camp gained the 1946 Fifteenth Air Force headquarters for bomber operations, and "Colorado Springs" had the 206th Army Air Force Base Unit organized on 6 June 1945 and initially controlled RBS detachments at Kansas City and Dallas Love Field (transferred in August to Mitchel Field as the 63rd AAFBU). A November 1946 US defense plan "recommended moving ADC Headquarters from Mitchel Field to a more central location…in a protected command center … designed to withstand attack by all foreseeable weapons" (e.g., "German A-4 type" missiles).

Air Force Base
In 1949 the installation was renamed Ent Air Force Base and the 15AF moved to March AFB  (the "HQ Sq, Fifteenth AF" arrived on 7 Nov 1949.)  On 10 November 1950, Generals Vandenberg and Twining notified General Whitehead that "the Air Force had approved activation of a separate Air Defense Command [from CONAC] with headquarters on Ent".

Air Defense Command
The ADC Major Command was re-established on 1 January 1951, the date the nearby Peterson Field was reactivated as a sub-base of Ent AFB. The former ADC headquarters at Mitchel Field began operations "in its new location, Ent Air Force Base," by 8 January 1951. Mitchel's Army Anti-Aircraft Artillery Command headquarters moved to one room at Ent in January 1951 and in February, the ARAACOM commander's staff began using the downtown Antlers Hotel until August 1953 (eventually moving to tbd street across from the site used for the 1963 Chidlaw Building.)

Ent's building used for the 1951 air defense command post 	was replaced in May 1954 with a "much improved 15,000-square-foot concrete block" Combat Operations Center (COC). By 1961, an image of the COC's "Plexiglass plotting board" was being transmitted to SAC's underground command post at Offutt AFB. The Ent AFB location was within city limits when Colorado Springs annexed an eastern area in tbd.

Continental Air Defense Command (CONAD) was "activated in Colorado Springs" after the Joint Chiefs of Staff agreed to establish a "joint service command for air defense". CONAD had "control of Air Force Air Defense Command forces, Army Anti-Aircraft Command forces, and Naval air defense forces" on 1 September 1954 (CONAD and ADC formally separated in 1956). Ent AFB had a golf course by 1954, and the Ent Rod & Gun Club had sanctioned trapshoots by 1958.

NORAD
In 1957 "on 6 September, CONAD advised all appropriate agencies that NORAD was to be established at Ent Air Force Base effective 0001 Zulu 12 September" with "integrated headquarters" of NORAD/CONAD/ADC and RCAF ADC. Colorado Springs had 1957 "monitor machines on the four DEW Line main circuits", and Ent became a "master station" of the 1958 Alert Network Number 1 (effective 10 June 1958, Colorado was the only state completely in the 34th NORAD Region.) Despite a 1958 JCS study group's recommendation that a new COC be in an Ent basement/sub-basement, the JCS on 18 March 1959 selected Cheyenne Mountain. After deployment of the Semi-Automatic Ground Environment computer network, Ent's command center received data from the AN/FSQ-8 centrals at Combat Centers. Adjacent to Ent's NORAD center was the SPADATS Operation Center with 496L Space Detection and Tracking System that began operations July 1961 in building P4's annex, a former hospital building.

Some of Ent's operations/units moved to the partially-underground 1963 Chidlaw Building ½ mi (¾ km) south-southeast of Ent. (e.g., the COC moved to the 1963 NORAD Combined Operations Center.) A cable between the Cheyenne Mountain nuclear bunker was connected with Ent AFB in April 1965, and the SPADATS mission remaining at Ent began the move to the Cheyenne Mountain "Group III Space Defense Center" in April 1966 (fully operational at 0001Z, 6 February 1967). ADCOM's Interceptor safety magazine was being published at Ent in 1968, and "12.28 acres" had been planned for closure in fiscal year 1974 (Ent Gun Club hosted the 1974 Armed Forces Skeet Championship.)

Ent Annex
Renamed the "Ent Annex" on April 1, 1975, the annex was assigned to the custody of Peterson AFB on 18 July 1975, and the installation was to be vacated by 30 June 1976. Fourteenth Aerospace Force inactivated at Ent on October 1, 1976--Fourteenth Air Force (Reserve) activated at Dobbins Air Force Base on October 8, 1976. Ent's off-base barracks (38.852°N, -104.7546°W) at 3920 Marion St (now E San Miguel St) were modified in the late 1970s for a retirement community and Ent Gun Club moved to Peterson Air Force Base.

Ent land totalling 35 acres was transferred in 1977 for the United States Olympic Training Center, and the golf course was sold c. 1977 to the city. For the 1979 ADCOM breakup, on 1 October Colorado Springs' 425th Munitions Support and 4614th Contracting squadrons were respectively reassigned to TAC and SAC (the 4603rd Management Engineering Flight was inactivated)—the ADCOM headquarters in the Chidlaw Building was "inactivated at Colorado Springs" on 31 Mar 1980.

Ent AFB Defense Area
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 Ent AFB Defense Area was designated a Formerly Used Defense Site.

Units
47th Communications Group, 1963 -1972 (to Peterson AFB)	 	615 Infirmary /615 USAF Dispensary (1958) 	 	1151st Special Activities Squadron 	 	Canadian Force Support Unit (1971)

Air Force Systems Command
 * Electronic Systems Division Detachment 10 (CMCO) 15 July 1963 –


 * Military Air Transport Service
 * 4th Weather Wing, c. 1965 – c. 1970


 * Strategic Air Command
 * Fifteenth Air Force
 * Headquarters, 15 September 1946 – 7 November 1949 (to March AFB)
 * 206th Army Air Force Base Unit

North American Air Defense Command

 * Headquarters, 12 September 1957 – 15 February 1963 (to Chidlaw Bldg)
 * Directorate of Command History (1960)
 * Office of Information, c. 1958 –
 * Space Intelligence Division

Continental Air Defense Command

 * Headquarters, 1954 September 1
 * Office of Information Services (1957) - tbd (to Chidlaw Bldg)


 * Army Anti-Aircraft Artillery Command/Army Air Defense Command
 * Headquarters, 15 January 1951 – 21 March 1957 – 1975
 * Headquarters staff, August 1953 – s
 * 8577th AAU (Administrative Area Unit)
 * Army Sec Joint Air Def Bd, 8621st AAU


 * Naval Forces CONAD (NAVFORCONAD), 1 September 1954 – 1 September 1965
 * Naval Administrative Unit (1966)


 * Air Defense Command/Aerospace Defense Command
 * Headquarters, 9 January 1951 – 15 January 1968 – tbd (to Chidlaw Bldg)
 * Communications-Electronics Directorate
 * "radar evaluation branch"
 * DEW System Office
 * Directorate of Historical Services (1956) /Historical Division (1964)
 * Office of Information
 * Directorate of Training
 * Institute Technical Division
 * Air Defense Personnel and Training Research Laboratory, December 1951 –
 * Field Printing Plant
 * Flying Safety Office
 * 9th Aerospace Defense Division, 15 July 1961 – 30 June 1968
 * 1st Aerospace Surveillance and Control Squadron/1st Aerospace Control Squadron, 6 February 1961 (transferred to the 9th on 1 Oct 61) – 1 July 1962 – tbd (to Cheyenne Mountain)
 * 2nd Surveillance Sq (Sensor), 1 February 1962 – 1 January 1967
 * 71st Surveillance Wing/71st Missile Warning Wing, 1 January 1962 – 1 January 1967 – 30 June 1968
 * 73d Aerospace Surveillance Wing, tbd – 31 December 1966
 * 4600 Air Base Group/4600th Air Base Wing headquarters, 1 January 1951 – 8 April 1958 – 18 October 1972 (to Peterson AFB)
 * 4600th Air Base Wing Security Police Squadron (1967)
 * 4600th Transportation
 * 4602nd Air Intelligence Service Squadron
 * 4603rd Management Engineering Sq, 1 October 1973 – 1 October 1979 (to SAC)
 * 4608th Support Squadron*, c. 1960 – c. 1972
 * 4614th Procurement Sq (1 April 1972-tbd)
 * 4616th Contracting Sq, tbd – 1 October 1979 (to SAC)
 * 5602nd Computer Services Sq (1 January 1972 - tbd)
 * Fourteenth Aerospace Force
 * Headquarters, tbd – 1 October 1976
 * Operations Staff (1971)
 * 71st Missile Warning Wing, 1 July 1968 – 30 April 1971
 * 73d Aerospace Surveillance Wing, 1 January 1967 – 17 July 1967