"Bleeding Kansas" refers to a period of violence in the mid-1850s during which Kansas Territory was the site of clashes between pro-slavery and anti-slavery forces. The conflict was sparked by the Kansas-Nebraska Act of 1854, which allowed settlers in the Kansas Territory to decide for themselves whether to allow slavery within their borders. Pro-slavery and anti-slavery settlers flooded into Kansas, each hoping to sway the outcome of the eventual vote. Violence erupted as the two sides clashed, resulting in a series of bloody incidents that left dozens dead and many more wounded. The conflict was eventually resolved when Kansas was admitted to the Union as a free state in 1861. The events of "Bleeding Kansas" played a significant role in the lead-up to the Civil War, and the conflict helped to further polarize the nation along sectional lines.