Osawatomie - the name derives from a combination of Osage and Pottawatomie - was settled in 1854 by Free-State families from the Ohio Valley and New England. John Brown, soon to become famous for his militant abolitionism, joined five of his sons at their homes near the new town in October 1855. By the spring of 1856, local defiance of Proslavery laws and officials was so notorious that 170 Missourians "punished" the area by looting Osawatomie. Two months later Free-State men destroyed a nearby Proslavery camp. On August 30 occurred the second battle of Osawatomie, in which a Proslavery force of 400 drove out the defenders, 40 men led by John Brown, and then plundered and burned the town. Among those killed that day was Brown's son Frederick.
At the John Brown Memorial Park in Osawatomie is the cabin of the Rev. Samuel Adair, Brown's brother-in-law, with whom he often stayed. The Republican party of Kansas was organized at Osawatomie in May, 1859, with Horace Greeley, famous editor of the New York Tribune, as the convention's principal speaker.