The Missouri Compromise of 1861 held the nation together by maintaining a fragile balance of slave states and free states. When settlers began moving into the Kansas and Nebraska territories, it threatened another imbalance between slave and free states. The proposed solution was the Kansas-Nebraska act, in which each territory would vote on whether to be slave or free. Politicians presumed that Kansas would vote to become a slave state and Nebraska a free state, thus continuing to maintain the balance.
Settlers from Missouri moved to Kansas, establishing many towns including Leavenworth, Lecompton and Atchison as slave state communities. Settlers from free states, many with the assistance of the abolitionist New England Emigrant Aid Company, established other towns such as Lawrence, Topeka, Osawatomie and Manhattan as free state communities. In 1855, Kansas held its first election for the Territorial Legislature. Thousands of "Border Ruffians" rode into the state, mainly from Missouri, and used fraud and intimidation to influence the election. Almost all the pro slavery candidates won, but the number of votes cast in the election was twice the number of eligible voters. The pro-slavery legislature became known as the 'bogus legislature' by free-state Kansans and relocated Lecompton.
Free-state Kansans formed their own legislature in Topeka and drafted the Topeka Constitution in 1855, which established Kansas as a free state. In July of 1856, pro-slavery president Franklin Pierce declared the Topeka legislature in insurrection and sent 500 federal troops to Topeka to forcibly disperse the free-state legislature.
Throughout the first half of 1856, hundreds of pro-slavery men had been entering Kansas, and many more free-state men arrived to oppose them. By the spring of 1856, rampant open violence had broken out. Numerous massacres occurred. Raiders from Missouri burned the Free State Hotel and two newspaper offices in Lawrence and the entire town of Osawatomie. John Brown, the same man who would later seize the arsenal at Harper's Ferry, led the free-state cause and retaliated with equal brutality. Finally, the new territorial governor, John W Geary, persuaded both sides to come to an uneasy peace.
In 1857, pro-slavery Kansans drafted the pro-slavery Lecompton Constitution. It was condemned by the largely anti-slavery US congress, but was supported by President James Buchanan. Congress declared this constitution invalid. Another election was held, which was widely boycotted by pro-slavery Kansans. The elected delegates drafted the anti-slavery Leavenworth Constitution. In 1859, the Kansas legislature re-affirmed Kansas's status as a free state by adopting the Wyandotte Constitution.
Sporadic violence continued until the outbreak of the Civil War. In the end, demographics determined that Kansas would be a free state. By the eve of the Civil War, there were simply more free-state citizens in Kansas than slave-state citizens. The pro-slavery US senate managed to keep Kansas from being admitted to the Union as a state until January of 1861. By this time the Civil War was only three months away.
The total number of deaths is estimated at from 56 to roughly a hundred plus that number. The end of the Border War is generally considered to be 1861, with the start of the Civil War. It didn't end, though, it simply merged into the greater conflict of the Civil War. The real violence along the border was just beginning.