The Missouri Compromise (1820): Settlers in Missouri requested admission into the Union, which caused conflict to arise. The United States consisted of 11 free states and 11 slave states, and the admission of Missouri into the union would upset this balance. Slaveholding states were accusing Northerners of trying to end slavery, and Northerners were accusing Southerners of planning to extend the institution into new territories, causing intense hostilities.
“This momentous question, like a firebell in the night, awakened and filled me with terror. I considered it at once as the knell of the Union. It is hushed, indeed, for the moment. But this is a reprieve only, not a final sentence.” —letter to John Holmes, April 22, 1820
The South Carolina Nullification Crisis (1832-1833): The high tariff on on manufactured goods forced the South to buy more expensive goods from Northerners. South Carolina saw the protective tariff as damaging to their economy, and began to question whether or not Calhoun cared about his states needs. To prove that he cared, he devised a nullification theory which questioned the legality of applying some laws to sovereign states. He believed that if the government did now allow the state to nullify a law, then the state could withdraw from the Union. The conflicts between the North and South would ultimately cause the Civil War, and lead South Carolina to become the first state to secede from the union.
The Wilmot Proviso (1846): The Wilmot Proviso meant that Utah, New Mexico, and California would be closed to slavery forever. The North was angry that Southern Congressmen refused to vote for internal improvements. Southerners were opposed to the proviso because they believed slaves were their property, which was protected by the Constitution. It prohibited any territory aquired in the war with Mexico from being open to slavery. This contributed to the Civil War because it ended the balance of free and slave states, as the number of free states would increase.
The Compromise of 1850: Clay tried to create a compromise that the North and South could both accept. He gained Webster's support, and presented the Compromise of 1850 which was a series of congressional measures that Clay hoped would settle "all questions in controversy between the free and slave states, growing out of the subject of Slavery". To please the North, it provided that California be admitted to the Union as a free state. To satisfy the South, the compromise proposed a more effective slave law.
The publication of Harriet Beecher Stowe's Uncle Tom's Cabin (1851-1852): A book created by Harriet Beecher Stowe that described the horrors of slavery. It delivered the message that slavery was a great moral struggle which caused the antislavery sentiment in the North. The novel infuriated the South, and argued that Stowe was uneducated about the plantation life and misinterpreted it. Approximately 300,000 copies were sold within the first year.
"So you're the little woman who wrote the book that made this big war." - Abraham Lincoln
The Kansas-Nebraska Act (1854): Douglas introduced a bill that would divide Nebraska in the North and Kansas in the South. It would repeal the conditions of the Missouri Compromise and establish sovereignty for both territories. It set up Kansas and Nebraska territories where the issue of slavery would be decided locallay. There was a bitter congressional debate over the bill which created petitions for and against the bill. It became a law in May 1854.
The Lincoln-Douglas Debates (1858): The topic of the debates was whether or not slavery could be extended into free territories. Douglas was a strong advocate for popular sovereignty, in allowing the citizens of a territory to vote for or against slavery. He believed it would allow slavery to pass away on its own. On the other hand, Lincoln spoke about the moral wrongs of slavery. He doubted that slavery would stop spreading without it becoming outlawed in the territories by the legislature.
John Brown's Raid on Harper's Ferry (1859): On October 16, John Brown led a band of 21 black and white men into Harper's Ferry, Virginia (West Virginia). His goal was to seize the federal arsenal there and start a rebellion by distributing the weapons to slaves. He was then convicted of treason, and was hung.
"I, John Brown, am now quite certain that the crimes of this guilty land will never be purged away but with blood"
The Election of Abraham Lincoln (1860): During the election of 1860, the Democratic Party split over the issue of slavery. Lincoln, Douglas, Breckenridge, and Bell were all candidates, however Lincoln emerged as the winner. He received less than half of the popular vote, and no electoral votes from the South. He denied that his plan was to interfere with slabery in places that it already existed while proceeding to oppose any expansion of territory. Southerners were convinced that his victory would cause a loss in their political voice in the national government.