Going to school in the South in the 70s and in the decades before that meant the correct answer was states rights, period. And I had a African American teacher too. She had been reciting the school board policy for so long I believed states WAS the correct answer for many years. The argument was that they fought for slaves to be counted in the their states population leading to more representatives in Congress. Slaves were worth in today's value worth about 20-50 thousand dollars each, they were fighting over the same things every other war was started over...money. But yeah it specifically says in a couple of states announcement of succession that it's TOTALLY over slavery.