US History/Friction Between States
Ideas and Questions of the Time 
The overriding question throughout the decade preceding the Civil War was, “Should slavery be allowed in the new territories of the United States?” Before 1848, the question had been hypothetical; however, with the new lands acquired during the Mexican War, it was time for America to make a firm decision regarding the expansion of slavery.
The central ideas dominating the debate were:
The Wilmot Proviso 
On August 8, 1846, Representative David Wilmot, a Pennsylvania Democrat, presented a proposal expressing that “slavery nor involuntary servitude shall ever exist in any part of any territory obtained from Mexico.” The Wilmot Proviso was never accepted as law, but it at long last put the issue forth on the political table.
The Calhoun Resolutions 
John C. Calhoun, the South Carolina statesman, responded with the Calhoun Resolutions, which said that Congress had no right to stop any citizen with slaves in their possession from taking those slaves into one of the territories. If they did so, the Fifth Amendment, which states that no person can be “deprived of life, liberty, or property, without due process of law,” would be violated. While this was not made formal legislation either, this belief became the standard in most of the south.
Popular Sovereignty 
A third option, which appealed to many moderates, most prominently Stephen A. Douglas of Illinois, was the idea of popular sovereignty. This was the idea of letting the settlers of a territory themselves decide whether slavery was to be allowed in it, by voting on state constitutions and other such measures. The primary merit of this initiative was that it took the debate out of Congress, which quickly grew tired of the issue, and put it into the hands of people it truly affected. There was also an unspoken understanding that most of the territories would end up being free, as most settlers that were already in those areas did not bring their slaves with them.
Compromise of 1850 
America looked to the Senate for an answer to the question of slavery within the territories. Henry Clay, nicknamed the "Great Compromiser," constructed a compromise: California was admitted as a free state, but all other territories in the Mexican Cession were allowed to choose between becoming a free territory or a slave territory. Also, as part of the Compromise, the slave trade was banned in the District of Columbia, and a Fugitive Slave Act was passed to allow the capture of fugitive slaves.
The Fugitive Slave Act was a very controversial measure. Previously, many in the North felt that slavery merely occurred in the South and that they had nothing to do with it. But under the Fugitive Slave Act, Northerners were required to help return runaway slaves. Thus, the Northerners felt that they were being dragged into aiding the institution of slavery. Several Northern states passed laws prohibiting their officials from aiding the enforcement of the Act.
While the admission of California as a free state gave the free states the majority in Congress, the pro-slavery measures in the Fugitive Slave Act made the Compromise seem more favorable to the South.
Uncle Tom’s Cabin 
Harriet Beecher Stowe’s Uncle Tom’s Cabin, published in 1852, is often called “the book that started the Civil War.” The melodramatic story of the evil overseer Simon Legree and his slaves Eliza and Uncle Tom painted an accurate picture of the horrors of slavery, and gave rise to much abolitionist feeling in the North. However, the effects were not easily visible from the start: because the country was growing tired of the sectional bickering over slavery, it took a while for the story to becoming embedded in the American imagination.
Nat Turner 
Nat, commonly called Nat Turner, (October 2, 1800 – November 11, 1831) was an American slave whose slave rebellion in Southampton County, Virginia, was the most remarkable instance of black resistance to enslavement in the antebellum southern United States. His methodical slaughter of white civilians during the uprising makes his legacy controversial, but he is still considered by many to be a heroic figure of black resistance to oppression. At birth he was not given a surname, but was recorded solely by his given name, Nat. In accordance with a common practice, he was often called by the surname of his owner, Samuel Turner.
Election of 1852 
In one of the less spectacular elections in American history, Senator Franklin Pierce of the Democratic party defeated General Winfield Scott of the Whig party. The Whigs tried to rely on Scott’s heroics as a general during the Mexican war to get him elected, a strategy that proved unsuccessful. Pierce, of New Hampshire, ended up being largely an ineffective president, trying and failing to please both the North and the South.
The Kansas-Nebraska Act and its Effects 
Throughout this time, plans were underway for a transcontinental railroad. A question arose as to what Eastern city should be the main terminus. Senator Stephen Douglas of Illinois hoped to advance his own state’s interests by making Chicago the railroad hub. To do this, he suggested a piece of legislation known as the “Kansas-Nebraska Act,” requiring recognition of two new territories, Kansas and Nebraska, west of Missouri and Iowa, respectively. These territories would both help his railroad and solve the overdue issue of the territories in the remainder of the Louisiana Purchase.
But to get the Kansas-Nebraska Act passed, he would have to get the support of Southerners, who wanted a railroad along a more southern route. For this reason, Douglas included in the Act the provision of popular sovereignty in the territories.
This blatantly violated the Missouri Compromise of 1821, which stated that slavery would be prohibited above the 36º30’ line. Douglas therefore opened himself up to the verbal barrage of protests from the North, who denounced the cancellation of the Missouri Compromise as unfair. Yet the Act passed, to the indignation of many Northerners, with the support of President Pierce.
The North 
Many in the North figured that if the Missouri Compromise was not an unbreakable law, neither was the Fugitive Slave Act, leading to many demonstrations against it. Boston witnessed the most remarkable of these, leading to many New Englanders turning against Pierce for his support of the Kansas-Nebraska Act.
Political Parties 
The Whig party essentially buckled under the pressure of the Kansas-Nebraska Act, with the North condemning it and the South supporting it. Whigs from the North joined some Democrats and Free Soilers that united under the general principle of the Wilmot Proviso, eventually calling themselves the Republican Party and offering its first presidential candidate, John C. Fremont in 1856.
"Bleeding Kansas" 
There was never much doubt that the settlers of Nebraska would, in the face of popular sovereignty, choose to bar slavery. Kansas, however, was another matter. Abolitionist and pro-slavery groups tried to rush settlers to Kansas in hopes of swinging the vote in the group's own direction. Eventually, both a free-state and a slave-state government were functioning in Kansas - both illegal.
Violence was abundant. In May 1856, a pro-slavery mob ransacked the chiefly abolitionist town of Lawrence, demolishing private property of the anti-slavery governor, burning printing presses, and destroying a hotel. Two days later, in retaliation, Abolitionist John Brown and his sons went to the pro-slavery town of Pottawatomie Creek and hacked five men to death in front of their families. This set off a guerilla war in Kansas that lasted through most of 1856.
Violence over the issue of Kansas was even seen in the Senate. Massachusetts Senator Charles Sumner accused South Carolinian Andrew Butler of having "chosen a mistress to whom he has made his vows - Slavery." Upon hearing these words, Butler's nephew, Representative Preston Brooks, walked onto the Senate floor and proceeded to cane Sumner in the head. Sumner suffered so much damage from the attack that he could not return to the Senate for over three years. Brooks was expelled by the House. Cheered on by southern supporters (many of whom sent Brooks new canes, to show approval of his actions), came back after a resounding reelection.
After much controversy and extra legislation, Kansas found itself firmly abolitionist by 1858.
Rachel v. Walker 
Rachel v. Walker was a lawsuit involving a slave who, in 1834, sued for her freedom from John Walker in the Supreme Court of Missouri, and won. This result was cited in 1856 in the famous Dred Scott v. Sandford case before the Supreme Court of the United States.
Dred Scott 
The question of the constitutionality of Congressional Compromises was decided by the Supreme Court in 1856. In "Scott v. Sanford", the Court ruled against a slave, Dred Scott, who had sued to become free. The Court ruled 7-2 that Scott remained a slave, and there were nine written opinions. The Chief Justice of the United States, Roger Taney, decided that blacks were so inferior that they could not be citizens of the United States, and that, consequently, they could not sue for his freedom (a state issue)in diversity in federal court, and therefore the court lacked jurisdiction. Nevetheless (the biggest "nevertheless" in American history) in a supererogatory effort to settle the question of slavery once and for all, the Marylander Taney ruled that the Missouri Compromise (which had banned the expansion of slavery into the territories north of Missouri) among other laws, was unconstitutional because it restricted the Constitutional right to own property. Many felt that Taney had committed a legal error in his decision. First, Taney had ruled that Scott had no right to sue. The case should have ended there. Taney had ruled on the constitutionality of the Missouri Compromise, which had, under Taney's own ruling that Scott had no right to sue, no bearing upon the case. Thus, the outrage against the Dred Scott decision was increased even more.
John Brown’s Raid 
John Brown, an extreme abolitionist last seen engineering the Pottawatomie Massacre in Kansas, came to the federal arsenal at Harper’s Ferry, Virginia for his last fight. He planned to take over the arsenal, give weapons to the slaves that would support him, and make a center of black power in the Appalachian Mountains that would support slave uprisings in the south.
The raid did not go quite as planned. Brown did take over the arsenal and took a couple of hostages, but ended up being assaulted by Virginia militia and U.S. Marines under the command of Col. Robert E. Lee of the US 2nd Cavalry. He was tried, convicted, and hanged for treason to the State of Virginia.
However, his Raid left a profound impact. John Brown became a martyr for the abolitionist cause during the Civil War. In the South, his actions gave cause to rumors of Northern conspiracy supporting slave insurrections, engendering further suspicion of outsiders in the South. A later Northern marching song sang “John Brown’s body lies a-mouldering in the grave, but his soul is marching on.”
In 1860, four major candidates ran for President. The Whigs, adopting the name "Constitutional Union", nominated Tennessean Senator John Bell. The Northern Democrats nominated Senator Stephen Douglas of Illinois and the Southern Democrats nominated the Vice President John Breckenridge of Kentucky. The more united Republican party nominated Abraham Lincoln, who spoke out against expansion of slavery. Though he assumed that, under the constitution, Congress could not outlaw slavery in the South, he assured all that he would work to admit only free states to the US. Due to divisions between the parties, Lincoln won the election by carrying every Northern State. Douglas won Missouri, Bell the Upper South, and Breckenridge the Deep South. The South was outraged. The North had a far larger population than the South, and thus had more electoral votes. The South had been out voted.