On May 19, 1858, approximately 30 border ruffians led by Charles Hamilton, a Georgia native and proslavery leader, crossed into the Kansas Territory from Missouri.

[4] The first commemoration at the site was two stone markers erected by men of the 3rd Iowa Cavalry Regiment in 1864, although these monuments had been destroyed by souvenir hunters by 1895.

[5] In response to the new opening, pro-slavery advocates known as border ruffians, many of whom were from Missouri, entered Kansas to illegally vote in an attempt to sway local elections.

The elections, which were held on March 30, 1855, resulted in a pro-slavery majority in the Kansas territorial government, who in turn created laws protecting slavery and among other things, outlawing abolitionist literature.

Later that month, John Brown, an abolitionist, led a group that murdered five pro-slavery southerners in a single night, an event that became known as the Pottawatomie massacre.

James Montgomery led a group of free-staters who fought with elements of the United States Army garrison of Fort Scott in the Battle of Paint Creek in April; one of the soldiers was slain in the action.

[7] On May 19, a border ruffian named Charles Hamilton led a group of about 30 men on a ride through the settlement of Trading Post.

[8] After taking 11 local free-staters hostage from their homes and fields, the border ruffians forced them into a nearby ravine and began shooting at them.

Land south of the ravine where the massacre occurred was owned by a local blacksmith, who later sold the site to Charles Hadsall, a friend of Brown.

In late June, Brown built a two-story log fort south of the ravine; Hadsall allowed him to keep a military post at the site.

[9] The incident horrified the U.S. and inspired John Greenleaf Whittier to write a poem on the murders, "Le Marais du Cygne", which appeared in the September 1858 The Atlantic Monthly.

[11] Commemoration of the massacre began in late October 1864, when men of the 3rd Iowa Cavalry Regiment erected two stone markers at the site, after the Battle of Mine Creek during the American Civil War.