Fort Riley, U.S. military post, 5,760 acres (2,331 hectares), NE Kans., on the Kansas River; est. 1852 to protect travelers on the Santa Fe Trail from attack by Native Americans. Located near the geographic center (though not the geodetic center) of the United States, it was first called Camp Center, but in 1853 it was renamed for Gen. Bennett Riley. It was a cavalry post and school until 1917, when it became a reserve-officer training center. Fort Riley is now a U.S. army staging and training area for transportation, supply, and service units.