In 1854 the Kansas-Nebraska Act split the Kansas territories into two states, Kansas and Nebraska, and decreed that “popular sovereignty,” in the form of a referendum by registered voters in the state, would determine whether any future states admitted to the union would allow slavery or not. Pro-slavery Missourians (known as “border ruffians”) poured into the territories, as did abolitionist supporters determined to prevent the spread of slavery. In the summer of 1856, proslavery forces attacked Lawrence, burning buildings, looting stores, destroying two newspaper offices, and beating residents. Hearing the news, John Brown and some supporters sought revenge by replicating the damage imposed on Lawrence in a small settlement of proslavery families along Pottawatomie Creek. The sacking of Lawrence and the murder and mutilation of five men at Pottawatomie Creek sparked a guerrilla war in Kansas that raged for months and cost some two hundred lives.