The war fought between the North and South in the United States was the Civil War, which occurred from 1861 to 1865. This conflict arose primarily from tensions over slavery and states' rights. The Southern states, which relied on an economy driven by slavery, seceded from the Union after the election of Abraham Lincoln. The war led to significant loss of life and devastation, as well as societal and political transformations. The Union's victory ultimately led to the preservation of the United States, the abolition of slavery through the Thirteenth Amendment, and significant changes in the roles of states and the federal government.