The site of Fort Sill was staked out by Major General Philip H. Sheridan in 1869 as a central place to defend Texas and Kansas settlements during the Indian Wars. Sheridan named the fort for his friend and former West Point classmate, Brigadier General Joshua W. Sill, who was killed during the Civil War.


In 1871, the General of the Army, William Tecumseh Sherman, as part of a country-wide Army post tour, was at Fort Sill and nearly killed during a quarrel with several Indians when he threatened to arrest them, although there was a peace policy ordered by President Grant.


The School for Fire for Field Artillery was founded at Sill in 1911 and continues to operate today as the U.S. Army Field Artillery School. Sill was also considered the first home to military combat aviation when the 1st Aero Squadron put together its own Curtiss JN-2 airplanes and made their first flights on August 10, 1915. However, two days later one of the planes crashed; the pilot was wounded and the passenger killed in front of a large group of onlookers. The squadron flew to Fort Sam Houston, TX, to help troop maneuvers along the U.S.-Mexico border in defense against spill-over from the Mexican Revolution, but after 500 missions the planes began to tire and just six weeks later they returned to Sill. They didn't fly again until World War I. Despite this initial setback, Sill has an enduring aviation legacy in the military world.


In 1917, Captain H. R. Eyrich established the Henry Post Army Airfield on the fort. By 1922, it was considered the busiest airport in the U.S. Post Field can be credited with the creation of numerous aviation units; many went on to be reassigned or inactivated, but some are still active today. 1917 also saw the introduction of the first balloon company which led to the Balloon Corps Training School at Post in 1918. Self-propelled balloons were developed here in 1937; unlike earlier balloons which had to be fixed to winch trucks by cables, the self-propelled type had attached baskets and could move around on their own.


The Field Artillery School took over Post Field in 1940 to train small plane pilots and had trained over 250 pilots and over 2,000 mechanics by the end of World War II. In 1945, Army Ground Forces Air Training School, later the Army Aviation School, was established at Post Field to train H25 and H13 helicopter pilots. The school was later transferred to Fort Rucker.


Fort Sill trains all field artillery soldiers and Marines in the U.S., including international students of Allied nations. It is home to the Field Artillery Training center which is the largest field artillery complex in the free world.