The following outline is provided as an overview of and topical guide to the American Civil War: American Civil War – civil war in the United States of America that lasted from 1861 to 1865. Eleven Southern slave states declared their secession from the United States and formed the Confederate States of America, also known as "the Confederacy." Led by Jefferson Davis, the Confederacy fought against the United States (the Union), which was supported by all the free states (where slavery had been abolished) and by five slave states that became known as the border states.