Bleeding Kansas refers to a violent series of events between 1854 and 1859 in the Kansas Territory and western Missouri. Stemming from a heated political and ideological dispute over the fate of slavery in the soon-to-be state of Kansas, the region saw a surge in electoral fraud, assaults, raids, and killings. Proslavery "border ruffians" and antislavery "free-staters" were the primary participants in this conflict, with estimates indicating up to 200 fatalities,^[11] though 56 were documented.^[12] This turmoil is often viewed as a precursor to the American Civil War.

Central to the conflict was the determination of whether Kansas would enter the Union as a slave or free state. This decision held immense significance at the national level, as the entrance of Kansas would tip the balance of power in the U.S. Senate, which was already deeply divided over slavery. The Kansas–Nebraska Act of 1854 stipulated that the matter would be settled by popular sovereignty, allowing the territory's settlers to decide. This ignited further tensions, as many proslavery sympathizers from Missouri entered Kansas under false pretenses to sway the vote. The political struggle soon devolved into a full-blown civilian conflict, marked by gang violence and guerrilla warfare. Parallel to this, Kansas experienced its own miniature civil war, complete with dueling capitals, constitutions, and legislatures. Both sides solicited external aid, with U.S. Presidents Franklin Pierce and James Buchanan openly supporting proslavery factions.^[13]

After extensive turmoil and a congressional investigation, it became evident that a majority of Kansans desired a free state. However, Southern representatives in Congress stonewalled this decision until many had left during the secession crisis that precipitated the Civil War. On January 29, 1861, Kansas was officially admitted to the Union as a free state. Even so, the border region continued to witness violence throughout the Civil War. The events of Bleeding Kansas showcased the inevitable nature of the conflict over slavery, highlighting the improbability of resolving sectional disagreements without violence and serving as a grim overture to the larger Civil War.^[14] Today, numerous memorials and historic sites honor this period.