The Missouri Compromise of 1820 closed all territory North of the 36°30' these territories would later be recognized as Nebraska and Kansas. It was understood that this territory would be closed to slavery as it was North of the 36°30.
Bleeding Kansas
New Mexico and Utah territories were organized in the Mexican Cession based on popular sovereignty, where congress passes the slavery question to settlers. Later on, the Kansas-Nebraska Act developed western lands and repealed the Missouri Compromise causing a National Controversy,
Caning of Charles Summer
Proslavery and antislavery settlers rushed into the territory to create a majority for their sides. Some proslavery were called "Border Ruffians" who crossed the Missouri Border for the election. As a result, violent confrontations began between the settlers.
Kansas Admitted as Free-State
I HEREBY DECLARE KANSAS A FREE-STATE
The "Bleeding Kansas" confrontations escalated, proslavery settlers were armed and committed several violent acts. The violence in Kansas continued for several years killing dozens of people.
Support no slavery!@#
MY HOUSE!!!
Caning of Charles Sumner became a polarizing incident, as Northerners condemned Preston Brooks as a violent Southern slaveholder. Southern supporters sent canes to Brooks in appreciation for his efforts to beat up the abolitionist senator with a cane.
Don't insult my state, you North trash.
NO PLEASE!!@
Kansas was admitted into the Union as a free state on January 29, 1861. Pro-slavery settlers drafted a constitution that would have established Kansas as a slave state. The Lecompton Constitution was blocked by the free-state majority in the House of Representatives.