Lincoln was anti-slavery, angering southern slavery states who wanted to secede from the Union. Lincoln hadn't even become president and seven states had seceded from the Union. They were South Carolina, Mississippi, Florida, Alabama, Georgia, Louisiana, and Texas.
John Brown was an anti-slavery radical who raided Harper's Ferry to give weapons to slaves. John Brown was caught, captured, and delivered the death sentence. John Brown believed that God had told him to stop slavery through bloodshed, and after telling this story to others was told to plead innocent of insanity. Brown stuck to his beliefs and died.
Dredd Scott case was about a slave in Illinois (an anti-slavery state) who decided to sue his owner because he was a slave in a non-slavery state. The court ruled that because Scott was black and a slave, he could not sue because he didn't have that right and that the slavery was legal because Scott was property in another state but moved to Illinois. The Harriet Beecher Stow books were written about the horrors of slavery and the hurt that the African Americans faced.
The Kansas-Nebraska Act approved the idea of popular sovereighnty, where states would vote to be slave or free, but this was ineffective because slavery Kansas population moved to anti-slavery Missouri to make Missouri slave, and fighting broke out at Lawrence Kansas, later called Bleeding Kansas.
Eli Whitney invented the cotton gin, which profited the South, which had to handpick seeds out of cotton. The cotton gin required manual labor, and the south cashed in on this manual labor cheap with slaves. The south economy depended on cotton, and the north economy depended on industry.