Answer:
After the election of Abraham Lincoln as president of the United States in 1860, South Carolina, followed by several southern states, decided to secede and separate from the United States to form a new nation, the Confederate States.
The reason why these states made this decision was because they suspected that President Lincoln had among its main government objectives the abolition of slavery, on which the southern states had organized their economies, based on agricultural exploitation through hand of slave labor. Assuming that the President would take this decision that would affect their lives and lead them to the economic and social debacle, South Carolina and other southern states separated from the United States, causing the Civil War.