On Dec 10, 1860, South Carolina asserted it's sovereignty as a free and independent State, and seceded from the union. Joining here were ten other brave States. Here you can read all the Ordinances of Secession, in Chronological order.
"Secession belongs to the different class of remedies. It is to be justified upon the basis that the States are Sovereign. There was a time when none ever denied it. I hope the time may come again, when a better comprehension of the theory of our Government, and the inalienable rights of the people of the States, will prevent any one from denying that each State is a Sovereign, and thus may reclaim the grants which it has made to any agent whomsoever."