Missouri Compromise of 1820: The admission of Missouri as a state in 1820 provoked a contentious national debate over slavery. Missouri was the second state to be carved from the vast territory acquired from France in the Louisiana Purchase and was to be admitted as a slave state. This aroused concern in the North. After much wrangling, a compromise was worked out. Under the terms of the Missouri Compromise, Maine was admitted as a free state at the same time that Missouri came in as a slave state, maintaining the balance between slave and free states. Additionally, Congress prohibited slavery in all western territories lying above 36 30' latitude (the southern boundary of Missouri). [Pauline Maier, Merritt Roe Smith, Alexander Keyssar, and Daniel J. Kevees, Inventing America: A History of the United States (New York: W.W. Norton, 2003), 332-33.]

Compromise of 1850: As a result of the Mexican War (1846-1848), the United States won vast acreage in the West (present-day California, Arizona, New Mexico, Nevada, Utah, and parts of Colorado and Texas). This acquisition renewed the controversy over slavery in the territories. California applied for admission as a free state in 1850. Southern political leaders were concerned that this would upset the balance of 15 free and 15 slave states. They also were disturbed by northern agitation to end slavery in the District of Columbia and by the passage of "personal liberty" laws in the northern states. The personal liberty laws aimed to restrict the cooperation of state officials in enforcing the federal fugitive slave law. Southern senators blocked the admission of California and a crisis was at hand. Prolonged negotiation finally produced a series of measures that became known as the Compromise of 1850. Aspects of the compromise included 1) admission of California as a free state; 2) a stronger fugitive slave law; 3) assurance that Congress would not interfere with the interstate traffic in slaves in the South; and 4) prohibition of the slave trade in the District of Columbia. Finally, an act allowed the citizens of the remaining territories to be carved out of former Mexican land to decide for themselves on allowing slavery. Optimists believed that these measures constituted a lasting settlement of the divisive issue of slavery, but this was not to be. [Maier, et al., 457-61.]

Kansas-Nebraska Act: In 1853-1854, the slavery issue got tied up with the effort to build a transcontinental railroad. In order to achieve territorial organization of land that a railroad to the West Coast might pass through, the Democratic Party had to make concessions to the South. The Kansas-Nebraska Act of 1854 gave the people of those territories the authority to decide on the legal status of slavery, effectively repealing the Missouri Compromise line. This act kicked off seven years of intense national dispute over slavery, culminating in secession and, finally, civil war in 1861. Northerners were outraged at the Kansas-Nebraska Act's repeal of a long-established compromise. Pro- and anti-slavery factions immediately converted the territory of Kansas into a bloody battleground.

Border Wars: The years of 1854-1861 were a turbulent time in Kansas territory. The Kansas-Nebraska Act of 1854 established the territorial boundaries of Kansas and Nebraska and opened the land to legal settlement. It allowed the residents of these territories to decide by popular vote whether their state would be free or slave. This concept of self-determination was called "popular sovereignty." In Kansas, people on all sides of this controversial issue flooded the territory, trying to influence the vote in their favor. Rival territorial governments, election fraud, and squabbles over land claims all contributed to the violence of this era.

Three distinct political groups occupied Kansas: pro-slavers, free-staters and abolitionists. Violence broke out immediately between these opposing factions and continued until January 29,1861, when Kansas entered the Union as a free state. This era became forever known in the state as "Bleeding Kansas."