12. Bleeding Kansas (1854-1859)
Between 1854 and 1859, the Kansas Territory was engulfed in violent confrontations between pro-slavery and anti-slavery settlers, collectively known as “Bleeding Kansas.” This turmoil was ignited by the Kansas-Nebraska Act, which allowed settlers to decide the slavery issue through popular sovereignty (nps.gov). The ensuing violence, including events like the Pottawatomie Massacre, served as a grim preview of the national conflict that would erupt into the Civil War.
