why did the civil war happen

The American Civil War happened primarily because of deep divisions between the Northern and Southern states over the issue of slavery. The Southern states wanted to preserve and expand slavery as it was central to their economy and social structure, while the Northern states opposed the expansion of slavery into new territories and increasingly supported abolition on moral and economic grounds. This conflict over slavery was intertwined with political power struggles, especially fears in the South about losing influence in the federal government after the election of Abraham Lincoln, who opposed slavery's expansion. Additional causes included disputes over states' rights—specifically the South's desire to assert authority to nullify federal laws they opposed—and tensions over territorial expansion, where the South wanted to spread slavery into new western lands, and the North did not. After Lincoln's election in 1860, Southern states felt politically marginalized and chose to secede from the Union, forming the Confederacy. The war began in 1861 when Confederate forces fired on Fort Sumter in South Carolina. The conflict was thus rooted in slavery, political power, economic differences, and sectional nationalism that made disunion and war inevitable.