The American Civil War was primarily fought over the issue of slavery. Tensions escalated between the Northern states, which were largely anti-slavery, and the Southern states, which relied on slave labor for their agrarian economy. The conflict, lasting from 1861 to 1865, aimed at preserving the Union and ultimately led to the abolition of slavery with the passing of the 13th Amendment. The war dramatically reshaped the social and economic fabric of the nation.