The various ordinances of secession of the Confederate States--along with the declaration of principles passed by the South Carolina legislature at the time of secession make it painfully clear that slavery was the paramount issue.
This is not Yankee pettifogging-- these documents are signed confessions!
The ordinances of secession were the actual legal language by which the seceded states severed their connection with the Federal Union. The declarations of causes, given elsewhere on this Web site, are where they tended to disclose their reasons for doing so, although only four states issued separate declarations of causes.
The political theory of the time among secessionists required that the act of secession be carried out by a specially elected convention or by referendum. In this sense the "secessions" of both Missouri and Kentucky were flawed, as neither was carried out in this manner. The Missouri secession ordinance was passed by a rump legislature and never approved by the people at large. The Kentucky secession ordinance was adopted by a convention of 200 participants representing 65 counties, held in Russellville.
These are offered in chronological order. If the state convention passed a declaration of causes document, then the header for that ordinance provides a link back to that document.
* South Carolina * Mississippi * Florida * Alabama * Georgia * Louisiana * Texas * Virginia * Arkansas * North Carolina * Tennessee * Missouri * Kentucky