The document summarizes key events leading up to the American Civil War. It discusses the Missouri Compromise of 1820 which balanced slave and free states, the Mexican Cession and attempts to ban slavery in the new territories, and the Compromise of 1850 which temporarily defused tensions over slavery. However, the Kansas-Nebraska Act of 1854 repealed the Missouri Compromise and led to violent clashes in Kansas between pro-slavery and anti-slavery settlers. The Dred Scott decision of 1857 found that Congress could not ban slavery and that slaves were property, not citizens. The Republican Party emerged opposing the spread of slavery. Abraham Lincoln was elected President in 1860 on the Republican ticket, leading southern states to se