Modern legislative skirmishes pale in comparison to the epic struggle over slavery. Congress fought one of its hottest antebellum battles over what to do with Kansas when the new nation sought to annex it. By giving residents of the new territory control over whether they would allow slavery, sponsors of the 1854 Kansas-Nebraska Act hoped to sidestep a showdown-by-proxy between North and South. Instead, they managed to create a real one: abolitionists and slavery apologists flooded the zone, forming armed guerrilla bands — including one led by abolitionist John Brown (above) — to vie for dominance. As the groups clashed, Congress scrambled to settle their future. Kansas finally entered the union as a free state in 1861. But it had pushed tensions to a snapping point: the Civil War erupted less than three months later.