The bloodiest single incident in the Kansas-Missouri border struggles, 1854-1861, occurred May 19, 1858, when about 30 Proslavery Missourians seized 11 Kansas Free-State men near Trading Post and marched them to a ravine 225 yards northwest of this marker. Lining up their prisoners, they callously shot them down, killing five and wounding five others. One escaped injury by feigning death. Northerners were horrified, and John Greenleaf Whittier immortalized the fallen in a poem, "Le Marais du Cygne."
A few weeks after the massacre John Brown arrived here and built a two-story log "fort," about 14 x 18 feet, which he occupied with a few men through the summer. In December he made a raid into Missouri in which 11 slaves were liberated and one man was killed. Brown's famous "Parallels," dated January 3, 1859, at Trading Post, pointed out that "hell is stirred from beneath" because of his raid while no comparable action had been taken to find and punish the Marais des Cygnes murderers.
A Brown follower, Charles C. Hadsall, bought this property in 1858. Later, adjacent to the site of the fort, he built the stone house which stands here today. The building and grounds were presented to the State of Kansas in 1941 by Pleasanton Post, Veterans of Foreign Wars.