The airfield was opened on 20 September 1941 as the Army Air Corps Basic Flying School, one of the fields utilized to meet the needs of the 30,000 Pilot Training Program. It provided basic air training for beginning pilots and crewmen. Many pilots and crews were trained here during the war including a number of Women's Air Service Pilots (WASPs).
Auxiliary air fields used by Merced Army Air Field during the war were:Merced Municipal Airport Auxiliary Field No. 1 37°20′01″N 120°30′30″W
Ballico Auxiliary Field No. 2 37°29′02″N 120°41′50″W
Howard Auxiliary Field No. 3 37°19′33″N 120°48′07″W
Athlone Auxiliary Field No. 4 37°11′37″N 120°21′41″W
Potter Auxiliary Field No. 5 37°08′17″N 120°31′59″W
Merced New Municipal Airport Auxiliary Field No. 6 37°17′12″N 120°30′58″W
Mariposa Auxiliary Field 37°30′40″N 120°02′21″W
With the end of the war 444th Bombardment Group (Very Heavy) arrived on 15 November 1945 from West Field, Tinian with four squadrons (344th, 676th, 677th, and 678th) of wartime B-29s. The 444th operated from Merced for about six months with the 678th BS being re-designated as the 10th Recon Squadron and its aircraft being converted to the RB-29 configuration.
The three B-29 squadrons inactivated at Merced on 6 May 1946 with the 10th Reconnaissance Squadron relocating to Davis-Monthan Field, Arizona where it turned in its RB-29 aircraft. The 444th was inactivated on 16 November 1947.
During the summer of 1945, when most other air fields were winding down, Merced was expanded to accommodate the large air tankers then programmed to come into service. After the war ended, Merced was home to several air tanker squadrons and remained a training center for pilots and air crews.
Merced Army Air Field was renamed Castle Field on 17 January 1946. It was named for Brigadier General Frederick W. Castle, who, on Christmas Eve 1944, remained at the controls of his burning B-17 Flying Fortress while his crew bailed out, and then died when the aircraft exploded.
The 93rd Bombardment Group (Very Heavy) was activated at Merced on 21 June 1946, starting a nearly 50-year relationship with the airfield. The 93rd was a former Eighth Air Force B-24 Liberator group which was assigned to Merced for Boeing B-29 Superfortress training. The 93rd was one of SAC's first ten bomb groups. There were three initial operational squadrons (328th, 329th, and 330th) which absorbed the equipment and aircraft of the inactivated 444th BG.
On 1 October 1946, the base was put on "minimal operations on caretaker status," with control of the facility under the Colorado Springs AAF. The 93rd Bomb Group, however remained active. It, along with the 509th Composite Group at Roswell Army Air Field, New Mexico, was all there was of Strategic Air Command at that time. The base remained in this status until 1 May 1947 when it was reactivated.
On 1 May 1947, Castle Field was reactivated under Strategic Air Command. On 28 July 1947, the 93rd Bombardment Wing, (Very Heavy) was established and took over responsibility from the group. During 1947–1948, it flew Boeing B-29 Superfortresses, but soon received the upgraded version of the B-29, the Boeing B-50 Superfortress. In 1948, the entire wing deployed to Kadena AB, Okinawa, becoming the first Strategic Air Command bomb group to deploy in full strength to the Far East.
Castle Field was renamed Castle Air Force Base on 13 January 1948 with the establishment of the USAF as a separate military service.
On 27 June 1949, the Air Force Reserve 447th Bombardment Group was activated at Castle and equipped with the B-29s formerly of the 93d Bomb Wing. The 447th remained active until 16 June 1951 when the group was activated and the aircraft and personnel sent to Far East Air Forces as replacements for combat losses during the Korean War. With the unit's departure, the 447th was inactivated.
The Convair B-36 Peacemaker entered SAC's inventory in 1948. The huge plane dwarfed the earlier bombers. The 93rd, along with all other B-29 and B-50 bomb groups, was re-designated "Medium." Only the B-36 groups were "Heavy."
The wing began aerial refueling operations in October 1950, providing aerial refueling and navigational assistance for the July 1952 movement of the 31st Fighter-Escort Wing from the United States to Japan, the first jet fighter crossing of the Pacific Ocean, during the Korean War. From 1953 to 1955, the wing flew Boeing KC-97 Stratofreighters. Jet propelled Boeing KC-135 tankers came on line in 1957.
The 93rd Bombardment Wing, Medium, received Boeing B-47s in May 1954, but its involvement with the new Stratojet was curtailed on 29 June 1955, when the wing received the first production line Boeing B-52B Stratofortress, making it the first SAC bomb wing to receive the new aircraft. The wing became SAC’s primary B-52 aircrew training organization, incorporating KC-135 aircrew training for refueling in mid-1956. For this purpose, it set up the 4017th Combat Crew Training Squadron which was supposed to handle all B-52 crew training for the next few years. When the mission of B-52 training became too great a task for just one squadron, the Wing's other three squadrons took over the flight training role and the 4017th assumed responsibility for ground instruction in 1956. The 93rd was SAC's primary B-52 training organization. The 93rd retained some of its B-47s until 1956 for crew training purposes. It was one of the few wings to have both jet bombers.
In November 1956 the wing made non-stop B-52 flights of some 16,000 nautical miles (29,600 km) around North America and to the North Pole.
Although most of the wing’s components were used for B-52 and KC-135 aircrew training between 1956 and 1995, one or more of its units sometimes participated in tactical operations, including aerial refueling.
From April 1968 to April 1974, the 93rd operated a special B-52 replacement training unit to support SAC’s B-52 operation in Southeast Asia. Also, the 328th and 329th Bomb Squadrons deployed to U-Tapao Royal Thai Navy Airfield, Thailand where they flew combat missions over Vietnam, Cambodia, and Laos during the Vietnam War.
The wing won the SAC Bombing and Navigation Competition and the Fairchild Trophy in 1949, 1952, and 1970, and the Omaha Trophy as the outstanding SAC wing in 1970.
In August 1990 the wing operated an aerial port of embarkation for personnel and equipment deploying to Southwest Asia during Desert Shield.
In addition to aerial refueling, Castle-based tankers ferried personnel and equipment, while B-52s deployed to strategic locations worldwide, including Saudi Arabia. B-52s bombed the Iraqi Republican Guard and targeted Iraqi chemical weapons, nuclear, and industrial plants during Desert Storm, January–February 1991. On 1 June 1992 the wing was relieved from SAC and reassigned to the new Air Combat Command.First jet aircraft nonstop flight around the world (January 1957).
Nonstop, unrefueled KC-135 flight from Yokota AB, Japan, to Washington, D.C. (April 1958).
The end of the Cold War brought many changes to the Air Force, and Castle AFB was selected for closure under the Defense Base Closure and Realignment Act of 1990 during Round II Base Closure Commission deliberations (BRAC 91).
On 1 June 1992 the 93rd was relieved from assignment to SAC and was reassigned to the newly formed Air Combat Command (ACC). It was then redesignated as the 93rd Bomb Wing and its B-52G aircraft given the ACC tail code of "CA" and carried blue tail stripes. The 328d Bomb Squadron was inactivated 3 May 1994, and the wing was placed on non-operational status.
However, the 93rd continued to supervise the closure of Castle AFB. The 93d Bomb Wing was inactivated on 30 September 1995 with the closure of Castle AFB. The Castle Air Museum remained at the site.
As of 2008, local government plans to convert the dormant facility to civilian commercial use has become an active political issue. It has been identified as the preferred location for the central maintenance facility of the proposed California High-Speed Rail system.
The University of California, Merced maintains a research site on the base, which was its first facility before construction of the main campus in Merced.
United States Penitentiary, Atwater stands on a portion of the grounds of the former Air Force Base.
In 2011, Google leased 60 acres in order to test the development of their new project, the self-driving car. Google is also leasing a hangar at the base in order to continue testing a new project, Project Loon. Project Loon is a program that creates an aerial Wi-Fi network, using balloons to loft relay equipment to high altitude. The Base is expecting Google to pay approximately $456,000 in rental fees for both of these projects over the course of one year. Base officials are excited for the attention the projects will bring not only to the base, but to Merced County as well.
In 1994 Igor Pasternak leased a hangar from the former Castle Air Force Base to build his Aeros 50, a seventy-eight foot long blimp for use in advertising. Pasternak subsequently moved his blimp building operation to Montebello, California.Army Air Corps Basic Flying School, Merced, CA, 20 September 1941 – 7 April 1942
Merced Army Flying School, 7 April 1942 – 8 May 1943
Merced Army Airfield, 8 May 1943 – 17 January 1946
Castle Field, 17 January 1946 – 13 January 1948
West Coast Air Corps Training Center, 20 September 1941
Re-designated: West Coast AAF Training Center
Re-designated: AAF West Coast Training Center, 1 May 1942
Re-designated: AAF Western Flying Training Command, 31 July 1943
Continental Air Forces, 1 July 1945
Re-designated: Strategic Air Command, 21 March 1946 – 1 June 1992
Air Combat Command, 1 June 1992 – 30 September 1995
Note: Base directed to revert to "minimum operations on caretaker status;' 1 Oct 1946; base under administrative control of Colorado Springs Army Air Base, Colorado, 1 Nov 1946-1 luI 1947. Reactivated from caretaker status, 1 May 1947
Ray Allen, a military child, was born at the base on 20 July 1975.