The Home of the Fighting First, the Big Red One, the 1st Infantry Division, Fort Riley dates back to 1853 when it was established as a safe point for settlers heading west on the Oregon, Santa Fe, and California Trails. The site was chosen by Captain Robert Chilton of the 1st Dragoons (now the 1st Cavalry) for its defensible location, strategically near the junction of the Republican and Smoky Hill Rivers. The post was named "Camp Center" because it was fairly near the middle of the United States. Shortly after construction was completed, the post was renamed Fort Riley after Major General Bennett C. Riley, a hero of the Mexican-American War.


The post has seen some notable figures and units. General George Custer was stationed at the fort during the late 1860s, as commander of the 7th Cavalry. The Custer House on post was named after him, and can still be visited to this day.


Fort Riley was also a post for the 9th and 10th Cavalry, the all-black Buffalo Soldiers of the late 19th Century. In 1887 Fort Riley gained the US Cavalry School, leading in time to the post become the "Headquarters of Cavalry." Even in the 1800s the Army was subject to base realignment, and while many other Army forts in Kansas were being closed due to reduced mission demand, Fort Riley remained open and generally increased in garrison. Riley became more and more central to US training in the Midwest, with Army, Reserves, and National Guard training on base. Fort Riley's cavalry training created a golden age for US horsemanship, which led to horse-mounted cavalry training persisting well into the 20th Century.


When the US entered World War I, a cantonment site, Camp Funston, was constructed five miles east of Fort Riley. It was used as a training center, and could house up to 50,000 people. After the war the camp was torn down, the lumber sold as scrap, and used as a maneuvering area.


During WWII, the fort was used as a P.O.W camp for German soldiers, and expanded with another 32,000 acres. About 125,000 soldiers trained there during the war; one notable trainee was an actor by the name of Mickey Rooney, another was heavyweight champion Joe Louis, both assigned to Special Services, the entertainment and morale branch. Most trainees were in some version of cavalry, true to the fort's roots, including the 9th Armored "Phantom" Division.


In 1955, the post became the home of the 1st Infantry Division, which prompted another 50,000 acres to be acquired to support the influx of troops and dependents. During the Cold War Fort Riley projected Army power to Vietnam, and several less intense deployments.


After the Cold War Riley troops deployed to the Gulf War to Kuwait and Iraq, and in the War on Terror to Iraq and Afghanistan. In 2005, as a result of the BRAC, the 1st Infantry Division units from Korea and Germany were relocated to Fort Riley. BRAC force adjustments have led to increased use of Fort Riley and its training centers, including much more advanced on-post simulations as well as practical field training and exercises.