Because it was more about protecting their primary source of income and not giving in to industrialization that took place in the Northern cities. Most southern states knew that industrialization would kill their primary sources of income.

It was never about slaves...just because the North were free-states doesn't mean that they didn't have slaves scattered about either. My thing is that the biggest reason that the North were free-states was because of industrialization, which would require a different type of man-power rather than an agricultural based economy. Slaves, like everyone said, was an add-on, and I think it was moreso an incentive for black people to fight for the Union rather than the Confederacy.

But did the South have a right to secede, I believe so...how it would've turned out would be a different matter altogether.