The 120th Fighter Squadron history can be traced back to June 27th, 1923 when the 120th Aero Observation Squadron was mustered into service as part of the Colorado Army National Guard. One year later, the 120th began flying the Curtis Jennies out of Lowry Field. The brand-new air field was named in honour of 2nd Lt. Francis B. Lowry who was shot down and killed near Crepion, France in 1918 while on a photographic mission. In later years, the unit would transition through a variety of more powerful observation aircraft such as the Douglas 0-2, Consolidated 0-17, and Douglas 0-38. The unit eventually started flying the 0-47-a three seat, all-metal, single-engine aircraft that took that unit into World War II.

Mobilization for World War II took place on January 6, 1941, 11 months prior to the bombing of Pearl Harbor. The unit, then 19 officers and 138 enlisted members, moved to Biggs Field, TX. It remained intact until the outbreak of the war when the 120th was disbanded and its members dispersed to share their knowledge and experience in the nations rapidly growing Air Corps.
In 1946, the 120th was reorganized and became a separate entity of the Colorado National Guard. That same year the unit became the first Air National Guard unit in the country to be federally recognized. Reborn as the 120th Tactical Fighter Squadron, the squadron began flying the P-51 Mustang.

The unit has been mobilized for World War Two, the Korean War, the Berlin Crisis, the Cuban Missile Crisis, the Pueblo Crisis, and Vietnam. As a result of the Pueblo crisis, the 120th spent 15 months on active duty, including a year at Phan Rang Air Base, Vietnam. The 120th FS was called upon again for Desert Storm, Northern Watch, and Southern Watch.