After the Battle of Lexington, the Post and Convalescent Hospitals were added to the training barracks, in order to assist in treating hundreds of incoming wounded troops.

Once the war ended, the barracks was dismantled, returning to its pre-war, civilian use as a fairground and race track.

In 1861, Major-General John C. Frémont assumed command of the Western Department of War for the Union Army.

By 1863, Benton contained over a mile of barracks, as well as warehouses, cavalry stables, parade grounds, and a large military hospital.

During the Civil War, under the administration of Emily Elizabeth Parsons, it was the largest hospital in the West.