From The Confederate and Neo-Confederate Reader:
Such a convention did meet, of course, in Charleston; in December 1860 it voted to take South Carolina out of the United States. As it did so, it indeed explained why, in a document titled “Declaration of the Immediate Causes Which Induce and Justify the Secession of South Carolina from the Federal Union.” The Declaration begins with a biased and incomplete history of the formation of the United States. Then it lists South Carolina’s grievances against the North: “We assert that fourteen of the States have deliberately refused, for years past, to fulfill their constitutional obligations, and we refer to their own statutes for the proof.” The only constitutional obligation that concerned South Carolina in 1860 was the fugitive slave clause, which the Declaration proceeds to quote. Delegates then note “an increasing hostility on the part of the non-slaveholding states to the institution of slavery.” The document immediately lists those states and the rights they tried to exercise to avoid being complicit with slavery: “The States of Maine, New Hampshire, Vermont, Massachusetts, Connecticut, Rhode Island, New York, Pennsylvania, Illinois, Indiana, Michigan, Wisconsin and Iowa, have enacted laws which either nullify the acts of Congress, or render useless any attempt to execute them. In many of these States the fugitive is discharged from service of labor claimed, and in none of them has the State Government complied with the stipulation made in the Constitution.”
(Emphasis added.) It was about slavery, slavery, and slavery. It was not about evil banks and corporate America, saving the bucolic paradise of the plantations from sprawl, or states rights. That only became the after-the-fact justification.
In fact, South Carolina apparently objected to 14 states exercising their “states rights.”