the people living within the territories should determine for themselves on the legality or illegality of slavery.

Later, the Kansas-Nebraska Act would expand popular sovereignty to apply to the Kansas and Nebraska territories. The result, however, was to generate turmoil and sectarian violence, as both abolitionists and defendants of slavery moved into Kansas in order to influence the vote. With the Dred Scott decision, the Supreme Court would weigh in on this question, defining slavery in terms of property rights, and ruling that Congress had no authority to legislate against it in the territories. This ruling greatly angered northerners, further intensifying the divisions within the country.

Lincoln's victory in the 1860 election would be answered with secession, leading to the start of the Civil War.

As the United States was expanding due to the acquisition of land in the 1840s, the federal government attempted to deal with the growing issue regarding the spread of slavery. The federal government tried to resolve the issue regarding the spread of slavery in the 1850s. The first attempt was when the Compromise of 1850 was made. The Compromise of 1850 allowed for California to enter the Union as a free state and banned the trading of slaves in Washington, D.C. It also allowed the people to decide if slavery would exist in the Utah and New Mexico territories. The Fugitive Slave Act was passed, which required northerners to help capture runaway slaves and return them to their owners in the South.

In 1854, the Kansas-Nebraska Act was passed. This law created the Kansas and Nebraska territories. It allowed the people to decide if slavery would exist in these territories. This law effectively ended the Missouri Compromise. It contributed to fighting in Kansas regarding whether Kansas would or would not have slavery.

These attempts to resolve the issue dealing with the spread of slavery were not successful in preventing the start of the Civil War in 1861.

The end of the Mexican War was both a blessing and a curse for the United States.  The nation gained a great deal of new territory, but it could not decide whether or not this new land would be free or slave.  Initially, David Wilmot proposed that the new land should be entirely free; of course, this was considered a dead letter in Congress and Southerners voted against this.  There was also talk of extending the Compromise of 1820 dividing line between free and slave territory, but this would split California in half. 

The solution, the Compromise of 1850, came from Henry Clay.  It was an omnibus bill, which meant that it had to be passed as a whole unit.  The bill ensured that California would come in as a free state, New Mexico Territory could vote on whether or not to have slaves, the slave trade would be ended in Washington D.C., and the North would tighten the Fugitive Slave Law.  The bill passed, but it really made no one happy.  California was filled with miners and merchants, most of whom did not own slaves.  New Mexico was too dry to support cotton without extensive irrigation, and slave owners in Washington could go to neighboring Virginia or Maryland to buy their slaves.  The Fugitive Slave Law meant that more federal dollars would be used to bring fugitive slaves back to the South.  There were problems with this, as slave catchers were paid a bounty for each slave returned, and there were instances of some free men being sold into slavery.  

Another solution was Stephen Douglas's Kansas-Nebraska Act which allowed the people who lived in these territories the right to vote on whether or not they could own slaves.  Kansas was soon filled by abolitionists and pro-slavery advocates, and a state of war existed there starting in 1858 as both sides tried to intimidate and kill each other.  

By the 1850s, especially after the 1852 publication of Harriet Beecher Stowe's Uncle Tom's Cabin, the polarization between abolitionists and pro-slavery parts of the population reached a fever pitch. Abolitionists wanted an end to slavery now, while the advocates of slavery began to ever more stridently insist that not only was slavery not a "necessary evil," it was a positive good that enhanced the lives of the slaves by providing cradle-to-grave security—and therefore should be protected and preserved.

Against that background, the fate of the states being formed as the result of the westward expansion was a tinderbox. Abolitionists wanted no more slavery allowed anywhere, anytime. Pro-slavery advocates wanted to spread the institution, fearing slavery in their own states would be choked off if too many states became free.

To solve the impasse, Congress passed the Kanas-Nebraska Act of 1854, which allowed citizens living in the newly settled areas to decide by vote whether their state would be slave or free. A seemingly fair solution, this turned out to be a disaster: both abolitionist and slavery supporters flooded into these areas, and clashes between them soon turned violent.

Slavery was a situation in which there simply was no arena for compromise. Both sides were completely dug in: to the abolitionists, slavery was unequivocally a moral evil that had to be abolished, and to the slave owners, it was an institution, that, at least to their minds, their survival depended on. The Kansas-Nebraska Act was a futile attempt at compromise that only hastened the nation toward the Civil War.