South Carolina officially seceded from the United States on December 20, 1860. South Carolina was the first state to announce it was no longer part of the Union and remained the only state to have officially seceded until January 9, 1861.
Because South Carolina was the first to act, it was also the first Southern state to call for a convention in order to form the Confederacy. South Carolina's decision to leave the United States was facilitated by the election of Abraham Lincoln as president of the United States. Within weeks of that election victory, the two South Carolina U.S. senators had submitted their resignation, and the events that created the Confederacy were set in motion.