With Lincoln’s election on November 6, 1860, South Carolina had had enough. On December 20, the state repealed its ratification of the U.S. Constitution and left the Union. By Lincoln’s inauguration, in March 1861, six other states had followed suit.
Congress had looked for ways to pacify the South. Days before Lincoln was sworn in, it passed a proposed 13th Amendment to the Constitution that would have permanently protected slavery from government control. But when Confederate guns fired their first shots at Fort Sumter on April 12, the proposed amendment was as good as dead. In the end, the 13th Amendment that the U.S. did add to the Constitution, in 1865, abolished slavery.
When war broke out, the eight other states that allowed slavery debated what to do. But when Lincoln called for troops to quell the rebellion, four of them (including Virginia, the largest) voted to join the Confederacy. The others—the “border states” of Maryland, Delaware, Kentucky, and Missouri—remained in the Union.