You do realize that it took an amendment to the Constitution before that happened, it didn't just fade away?
Or that had it remained legal eventually it would have required an amendment anyway to end slavery. The whole idea that Slavery would have ended on it's own any way, negates the very reasons for the democrat's rebellion against The United States, by your logic there was no reason to rebel in the first place.
Yeah I know "states rights", states rights to what? maintain slavery as an institution? Let me make this real simple for everyone that thinks this wasn't about slavery.
Show me one southern state in 1860 that wasrun by Republicans and seceded from the United States for the purposes of abolishing slavery as it existed in the Constitution, show me just one, that's all I ask and if you can, I'll admit defeat honorable.