South Carolina's Declaration of Secession was a formal document adopted on December 20, 1860, in which the state declared its intention to withdraw from the Union. This declaration was significant as it marked the first instance of a state seceding from the United States, setting off a chain reaction of secessions by other Southern states and escalating tensions that would lead to the Civil War. The declaration articulated grievances over issues such as states' rights and the perceived threat to slavery.