In response to the election of Abraham Lincoln to the presidency of the United States on a political platform that opposed the expansion of slavery, South Carolina seceded from the Union on December 20, 1860. Six more states would follow in the ensuing months: Mississippi, Florida, Alabama, Georgia, Louisiana, and Texas. In February 1861, they formed the Confederate States of America, an entity considered illegal by the United States government. On April 12, 1861, Confederate forces attacked Fort Sumter, a Union fort in the harbor of Charleston, South Carolina. This began the first battle of the deadliest conflict in US history, the American Civil War. This primary source set uses documents, illustrations, and maps to explore events and ideas that drove the formation of the Confederate States of America and the United States’ descent into civil war.