The Kansas-Nebraska Act of 1854 created the territories of Kansas and Nebraska, repealed the Missouri Compromise of 1820, and allowed settlers to decide whether to allow slavery within their boundaries.

Although the Kansas-Nebraska Act initially aimed to create opportunities for a transcontinental railroad, it instead helped spark the Civil War, which would occur years before a transcontinental railroad was completed.

For more than 30 years before the organization of Kansas and Nebraska as territories, the slavery question had been a “bone of contention” in the halls of Congress. Missouri’s first petition for admission into the Union in March 1818 started the agitation that culminated in the passage of the Missouri Compromise on March 6, 1820.

Section eight of the Missouri Compromise provided “That in all that territory ceded by France to the United States, under the name of Louisiana, which lies North of 36° 30′ North latitude, not included within the limits of the state contemplated by this act, slavery, and involuntary servitude, otherwise than in punishment of crimes of which the parties shall have been duly convicted, shall be, and is hereby, forever prohibited.”

Of the original 13 states, seven were free, and six were slave states. From the adoption of the Constitution to 1819, five slave states — Kentucky, Tennessee, Louisiana, Mississippi, and Alabama — had been admitted into the Union, while during the same period, four free states — Vermont, Ohio, Indiana, and Illinois — had been added, so that in 1819, immediately after the admission of Alabama, there were 11 of each. The admission of Maine in 1820 gave the free states a majority of one, but the equilibrium was again restored by the admission of Missouri in 1821. This equality policy was maintained for the next 20 years, except for short intervals. Arkansas, a slave state, was admitted in 1836, but was followed by the free state of Michigan in 1837. The admission of Texas and Florida in 1845 gave the slave power a slight advantage, which was regained by the free states with the admission of Iowa in 1846 and Wisconsin in 1848.

By that time, nearly all available territory south of the Missouri Compromise line had been divided into states, and slaveholders were compelled to look for new territory if they wanted to extend the institution. After a heated debate that lasted eight weeks in the first session of the 31st Congress over the admission of California, Henry Clay, on January 29, 1850, introduced the resolution that formed the basis of the celebrated “Omnibus Bill,” or compromise measures of 1850. These resolutions and the bill that followed provided for the admission of California “without the imposition by Congress of any restrictions in respect to the exclusion or introduction of slavery within those boundaries.” With the admission of California as a free state, which made 16 free states to 15 slave states, the slave power was driven to desperation. Soon, the region West of the Missouri River began to organize into territories, and as all this section lay North of a line of the Missouri Compromise, the cry went up for its repeal.

Petitions were received in the first session of the 32nd Congress, in 1851-52, to erect a territory West of the Missouri River, but no action was taken. The first real effort in Congress to organize a territory, including the states of Kansas and Nebraska, was made on December 13, 1852, when Willard P. Hall, a member from Missouri, introduced a bill providing for the organization of the “Territory of Platte” to include both the present states of Kansas and Nebraska.

However, nothing came of this bill, and more bills were submitted, argued, and rejected over the next year. On January 23, 1854, Senator Stephen Douglas of Illinois submitted a substitute bill that provided for two territories instead of one—the northern territory to be called “Nebraska” and the southern one “Kansas.” Douglas hoped to gain Southerners’ support under the presumption that the more northern territory would oppose slavery while the South would permit it. This gave rise to the term “Kansas-Nebraska Bill,” which quickly became a familiar expression nationwide.

A long, bitter debate followed, but Congress passed the act, and President Pierce signed it on May 30, 1854, opening the territories of Kansas and Nebraska. The Kansas-Nebraska Act infuriated many people in the North, who considered the Missouri Compromise a long-standing, binding agreement. Still, it was strongly supported in the pro-slavery South, which saw it as an opportunity to make Kansas a slave state. Southerners and pro-slavery men, mainly from Missouri, soon flooded Kansas, intending to vote for slavery. Alternatively, abolitionists and Emigrant Aid Societies came from the North to ensure the state would reject slavery.

For the next seven years, an internal civil war would be fought in Kansas over the issue, resulting in the territory earning the nickname “Bleeding Kansas” as the death toll rose. Eventually, the anti-slavery settlers outnumbered pro-slavery settlers, and on January 29, 1861, just before the Civil War, Kansas was admitted to the Union as a free state.