Bleeding Kansas, Bloody Kansas or the Border War was a series of violent civil confrontations in the United States between 1854 and 1861 which emerged from a political and ideological debate over the legality of slavery in the proposed state of Kansas. The conflict was characterized by years of electoral fraud, raids, assaults, and retributive murders carried out by pro-slavery "Border Ruffians" and anti-slavery "Free-Staters" in Kansas and neighboring Missouri.
https://en.m.wikipedia.org/wiki/Bleeding_Kansas