1. Sectionalism: The United States was divided into two distinct regions: the North and the South. The North was predominantly industrial, while the South was agrarian. Differences in economic and social systems led to political conflict between the two regions.
2. States' Rights: The Southern states believed in the concept of states' rights, which meant that each state had the right to make its own laws and govern itself. They feared that the federal government was becoming too powerful and encroaching on their autonomy.
3. Slavery: Slavery was a particularly contentious issue between the North and the South. The Northern states had gradually abolished slavery, while the Southern states relied heavily on slave labor for their agricultural economy. The expansion of slavery into new territories became a major point of contention, leading to the debate over slavery in the territories gained from the Mexican-American War.
4. The Election of Abraham Lincoln: The election of Abraham Lincoln, who was opposed to the expansion of slavery, in 1860 was the final straw for Southern states. They saw his victory as a threat to their way of life and began the process of secession, forming the Confederate States of America.
Therefore, the Civil War was caused by a combination of sectionalism, states' rights, slavery, and political tension between the North and the South.