What event in 1860 caused southern states to secede?

The election of Abraham Lincoln in November 1860 was the pivotal event that prompted several southern states to secede from the Union. Lincoln, representing the anti-slavery Republican Party, was perceived by many in the South as a threat to the institution of slavery and their way of life. In response, states like South Carolina began seceding in December 1860, ultimately leading to the formation of the Confederacy and the onset of the Civil War.