Fighting broke out in April 1861 when the Confederate army began the Battle of Fort Sumter in South Carolina, just over a month after the first inauguration of Abraham Lincoln. After Confederate forces seized numerous federal forts within territory they claimed, the attempted Crittenden Compromise failed and both sides prepared for war. An initial seven Southern slave states declared their secession from the country to form the Confederacy. Disunion came after Abraham Lincoln won the 1860 United States presidential election on an anti-slavery expansion platform. The practice of slavery in the United States was one of the key political issues of the 19th century decades of political unrest over slavery led up to the war. On the eve of the Civil War in 1860, four million of the 32 million Americans (nearly 13%) were enslaved black people, almost all in the South. The central cause of the war was the status of slavery, especially the expansion of slavery into territories acquired as a result of the Louisiana Purchase and the Mexican–American War. The American Civil War (Ap– May 9, 1865, also known by other names) was a civil war in the United States fought between the Union states (-states remaining in the federal union- or 'the North') and the Confederate states (- southern states that voted to secede- 'the Confederacy' or 'the South').
