No, it wasn't.
If it was truly about States' Rights, then states wouldn't have been forced under the CSA Constitution to allow slavery.
The Civil War was about a lot of things, but States' Rights was not among them.
Are you kidding me? The states willfully joined the Confederacy knowing the conditions involved; and most if not all of them already allowed slavery, anyway.
HAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA
It was about both.
The general issue was States Rights.
The particular issue was Slavery.
It could have been about taxation (Cf. Whiskey Rebellion) or any other conflict that had arisen and continue to arise between the States and the Federal Government.
Even today we are paying the price for the South choosing such low moral ground to test such an important Constitutional principle.
That's very true and not widely known.
Article I, Section 9, Clause 4: No bill of attainder, ex post facto law, or law denying or impairing the right of property in negro slaves shall be passed.
“The Civil War was about a lot of things, but States’ Rights was not among them.”
Total BS. Get a history book.
If you've never read the Confederate Constitution (and one could draw that conclusion from your comment), I'll be happy to provide a link to that neoConfederate organization, Yale University. http://www.yale.edu/lawweb/avalon/csa/csa.htm
Or, if you prefer a short summary, the Confederate Constitution (unlike the Yankee one) prohibited the importation of slaves from other parts of the world, permitted, but did not require, laws prohibiting the importation of slaves from the United States, required that slavery be permitted in any new territory, and protected property rights of Confederate citizens as they moved from state to state within the CSA.