Established by Major W. J. Hardee, 2nd U.S. Cavalry, on January 3, 1856 for the purpose of defending the frontier against the Comanche Indians. Named in honor of Samuel Cooper, Adjutant General, U.S. Army. Home of General Robert E. Lee for nineteen months, 1856-1857. From this post the Cimarron Expedition set out, October 1, 1859. Abandoned February 21, 1861. Erected by the State of Texas 1936