The application of popular sovereignty to the organization of the Kansas and Nebraska territories ended the sectional truce that had prevailed since the Compromise of 1850. After several months of rancorous debate, Congress passed five laws—known collectively as the Compromise of 1850—that people on both sides of the divide hoped had solved the nation’s problems.

Many Americans, both Black and White, flouted the Fugitive Slave Act by participating in the Underground Railroad, providing safe houses for freedom-seekers on the run from the South. The act also upended the second party system of Whigs and Democrats by inspiring the formation of the new Republican Party, committed to arresting the further spread of slavery.

popular sovereignty — the principle of letting the people residing in a territory decide whether or not to permit slavery in that area based on majority rule. Underground Railroad — a network of free Black and northern White people who helped enslaved people escape bondage through a series of designated routes and safe houses. Compromise of 1850 — five laws passed by Congress to resolve issues stemming from the Mexican Cession and the sectional crisis. Republican Party — an antislavery political party formed in 1854 in response to Stephen Douglas’s Kansas-Nebraska Act.