Which state was the first to secede from the union in on what grounds?

South Carolina was the first state to secede from the Union on December 20, 1860. The secession was primarily driven by concerns over states' rights and the perceived threat to slavery posed by the election of President Abraham Lincoln, who was seen as opposed to the expansion of slavery into new territories. South Carolina's leaders argued that the federal government was infringing on their rights and their way of life.