The American Civil War (1861–1865), also known as the War Between the States and several other names, was a civil war in the United States of America. Eleven Southern slave states declared their secession from the U.S. and formed the Confederate States of America (the Confederacy). They fought against the "Union", which included all of the free states and the five slaveholding border states. The Union was led by Abraham Lincoln and the Republican Party; the Confederacy was led by Jefferson Davis. The Confederacy attempted secession because Republicans opposed the expansion of slavery into territories owned by the United States, and Lincoln's victory in the presidential election of 1860 resulted in seven Southern states declaring their secession from the Union even before Lincoln took office.^[1] The Union rejected secession, regarding it as rebellion.