The conflict between the North and South in the United States, known as the American Civil War, was primarily caused by differences over slavery, states' rights, and economic disparities. The Southern states, heavily reliant on an agricultural economy supported by slavery, sought to maintain their way of life, while the Northern states, which were more industrialized and favored abolition, pushed for a more unified national policy against slavery. Tensions escalated over issues like the expansion of slavery into new territories and the election of Abraham Lincoln, leading to secession and armed conflict from 1861 to 1865.