Bleeding Kansas, Bloody Kansas, or the Border War, was a series of violent civil confrontations in the Kansas Territory, and to a lesser extent in western Missouri, between 1854 and 1859. It 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 murders carried out in the Kansas Territory and neighboring Missouri by proslavery "border ruffians" and retaliatory raids carried out by antislavery "free-staters". According to Kansapedia of the Kansas Historical Society, 56 political killings were documented during the period, and the total may be as high as 200. It has been called a "tragic prelude", or an overture, to the American Civil War, which immediately followed it.