The Army built Randolph AFB, the showplace of the Air Force, on a tract of land just outside what is now Universal City. The need for Randolph began soon after the enactment of the Air Corps Act of 1926. The act, which changed the name of the Army Air Service to the Army Air Corps, provided a five-year expansion program for the under strength Air Corps, and established two new brigadier general positions for the Army. One of these new positions placed a general officer in charge of all flying training for the Air Corps. Brigadier General Frank P. Lahm, later known as the "Father of Randolph Field," filled this position first. General Lahm soon realized he needed another air field dedicated to flying training when the training requirements of the Air Corps grew too great for Brooks and Kelly Fields alone. The initial site chosen for the new field was a place known as Calf Hill, located less than 10 miles east of the city on Hedwig Road, just south of the present site of Woodlake Country Club. However, because an essential tract of land could not be obtained, and speculation caused prices to rise, General Lahm dismissed the site. In November 1927 another 19 sites were submitted to General Lahm for his consideration. Finally, Lahm selected a 2,300-acre tract near Schertz for the new field.

In December 1927, the city of San Antonio sought appropriations in Washington for the field, but found a Congress not in a buying mood. The government already owned suitable land in Florida and California. Additionally, other cities vying for the new field lined up to give land free to the government, so San Antonio needed to act fast. Within a couple of weeks, the city council devised a plan to purchase the land. San Antonio notified Congress on 31 December 1927 that it had land available to give the Air Corps as a gift. The War Department accepted the land in August 1928.
Randolph Field During the search for a new training field, a young first lieutenant named Harold Clark busied himself designing his ideal "Air City" on the back of dispatch sheets while assigned as a dispatch officer at the Kelly Field motor pool. Prior to entering the Army, Lieutenant Clark trained as an architect and he designed an airfield unlike any already built. Clark's design centered the building area on the field, laid out the streets concentrically, and put the aircraft ramps and runways on three sides forming a square perimeter around a circular building layout. Clark took his drawings to General Lahm to consider for the new field. Impressed with the lieutenant's designs, Lahm assigned Clark to his office in December 1927, so the lieutenant could devote full time to developing his design.
After the site for the new field was selected, a committee of officers was organized to select a name for the new installation. Membership of the committee included Capt William M. Randolph, a native of Austin and Adjutant of the Advanced Flying School at Kelly. While serving on the committee, Captain Randolph died in aircraft accident. While on a return flight to Kelly, his AT-4 crashed on takeoff from Gorman Field, Texas, likely due to strong winds. A member of the committee suggested the new field be named for Randolph. Randolph Field was formally dedicated in front of a crowd in excess of 15,000 people on 20 June 1930. Captain Randolph's widow, Mrs. Cornelia Read Randolph, raised the first flag over the base.
On 1 October 1931, the Air Corps Training Center moved its headquarters to Randolph. A month later, on 2 November 1931, the first pilot training class of 210 Flying Cadets and 99 student officers began their primary pilot training. Student officers identified personnel already in the Army. West Point graduates and line officers who transferred to the Air Corps represented most student officers, but students also included enlisted pilot trainees, and reserve and National Guard officers. Flying Cadets (renamed Aviation Cadet in 1941) encompassed those with no prior military service. The military training for cadets modeled the programs at West Point and Annapolis. In fact, Randolph quickly became known as the "West Point of the Air," and getting accepted into the program was difficult. Most applicants failed to make it through the initial screening process. Those who did make it to Randolph went into an intense eight month-long program consisting of primary and basic pilot courses, of which half would make it through.

Primary training continued at Randolph until 1939 when the Air Corps contracted primary out to civilian schools, and the mission shifted to basic pilot training. Cadet training at Randolph continued until March 1943, when the Army replaced it with the Central Instructor School. For the next few years, the mission at Randolph turned to training instructors for all three phases (basic, primary, and advanced) of the flying training program. During this time, the Central Instructor School trained 15,396 pilots as instructors. Since that time pilot instructor training remained a central part of Randolph's mission.
Cadets in Flight Training
In September 1947 the Air Force became a separate service. Effective 13 January 1948, it renamed its major installations as air force bases. The outbreak of the Korean War rushed B-29 Combat Crew Training to Randolph due to the need for bomber crews overseas. Basic pilot training at first moved to the west runway to make room for the B-29, but eventually transferred to Craig AFB, Alabama. From 1950 until 1956--when B-29 training ended at Randolph--21,519 crewmembers graduated. Other training during the 1950s included C-119 instrument training, KC-97 and B-57 crew training, and the USAF Helicopter School. A number of facilities were also constructed during this period, including Wherry housing, an annex to the base elementary school (August 1954), and Chapel #2 (April 1955). Between July and October 1957, Air Training Command (redesignated Air Education and Training Command in 1992) moved its headquarters from Scott AFB, Illinois, to Randolph.

In the early 1960s, new training aircraft began arriving at Randolph. The T-38A and T-37A arrived in 1961 and 1965 respectively, and replaced the older T-33 and T-34. The T-39 also arrived in 1961, for use in instrument training, and remained until 1989. During the same time, Randolph gained two new residents, the Air Force Military Personnel Center (now Air Force Personnel Center) and the USAF Recruiting Service (now Air Force Recruiting Service).

Shortly after the end of the Vietnam War, Air Training Command established a pilot requalification training course for over 150 USAF pilots held prisoners of war. Operation Homecoming began on 2 May 1973 and ended on 12 November 1976. After that, Randolph entered a long period of stability until the 1988 BRAC brought Navigator training to Randolph in 1992, along with a fleet of T-43s to support it as a flying classroom. Navigator training became joint training with the Navy in the 1990s. Despite a two year period when it transferred to Pensacola, Florida, joint navigator training it remained at Randolph. In 1999, Electronic Warfare Officer training arrived at Randolph. In 2004, Air Force navigators and electronic warfare officer combined to become a single Combat Systems officer. The 2005 BRAC transferred Combat Systems Officer training to Pensacola.

In 1993, the T-1A arrived to train instructors to prepare student pilots for assignments to airlift and tanker aircraft, as did Introduction to Fighter Fundamentals training and a fleet of AT-38s (a T-38A modified to drop a practice bomb). Introduction to Fighter Fundamentals departed Randolph in 2001, only to return in 2007. During the 2000s, the Air Force upgraded all AT-38s and T-38As to T-38C models and Randolph received theirs in 2004. Randolph also gained a fleet of the brand new T-6A in 2000, which replaced the outdated T-37, the last of which flew out in 2007.