Are you sure they were individually founded on it? I thought they just used it as a excuse to secede and form the Confederacy.
Yes. I'm on my phone so copying and pasting is hard but check out the Mississippi declaration:
"Our position is thoroughly identified with the institution of slavery-- the greatest material interest of the world. Its labor supplies the product which constitutes by far the largest and most important portions of commerce of the earth. These products are peculiar to the climate verging on the tropical regions, and by an imperious law of nature, none but the black race can bear exposure to the tropical sun. These products have become necessities of the world, and a blow at slavery is a blow at commerce and civilization. That blow has been long aimed at the institution, and was at the point of reaching its consummation. There was no choice left us but submission to the mandates of abolition, or a dissolution of the Union, whose principles had been subverted to work out our ruin."
This is crazy racist and clearly pro-slavery. It was the issue of states rights that drove the secession but it was about their right to impose slavery on a state by state basis without federal interference.