The start of the American Civil War in 1861 was primarily triggered by the issue of slavery and states' rights. Tensions had been rising for decades as the country grappled with conflicts over the expansion of slavery into newly acquired territories. The election of Abraham Lincoln in 1860, who opposed the further spread of slavery, led several Southern states to secede from the Union, forming the Confederate States of America. The war began in earnest when Confederate forces attacked Fort Sumter in South Carolina in April 1861. This conflict ultimately aimed to determine the future of slavery and the balance of power between federal and state governments.