On January 8, 1869, MG Philip H. Sheridan staked out the site that would become Fort Sill. Sheridan was leading a campaign into Indian Territory to stop hostile tribes from raiding border settlements in Texas and Kansas. His massive winter campaign involved six cavalry regiments accompanied by frontier scouts "Buffalo Bill" Cody, "Wild Bill" Hickock, Ben Clark, and Jack Stillwell. Troops from the 10th Cavalry, a distinguished unit of black "Buffalo Soldiers" who constructed many of the stone buildings still surrounding the Old Post Quadrangle, camped at the new fort.

Fort Ord was established in 1917, originally as Camp Gigling, as a military training base for infantry troops. In 1917, the US Army bought the present day East Garrison and nearby lands on the east side of Fort Ord to use as a maneuver and training ground for field artillery and cavalry troops stationed at the Presidio of Monterey. & Before the Army's use of the property, the area was agricultural, as is much of the surrounding land today. No permanent improvements were made until the late 1930s, when administrative buildings, barracks, mess halls, tent pads, and a sewage treatment plant were constructed. This facility was designated as Camp Ord in 1939 and became Fort Ord in 1940. In 1938, additional agricultural property was purchased for the development of the Main Garrison.