Texas' articles of secession name slavery as a main cause twelve times. Georgia's calls abolitionism "heresy" and Mississippi, bless them, referred to it with "a blow at slavery is a blow at commerce and civilization," before going even further with such quotes as
[The US government] refuses the admission of new slave States into the Union, and seeks to extinguish it by confining it within its present limits, denying the power of expansion.
It tramples the original equality of the South under foot.
Which I am only leaving here because somebody wrote that, meant it, and sent it off, and it is insane to read.
Fortunately for Mississippi, their constituents can't.