Paul, I'm sorry, but the war was fought over slavery. Yes, the North didn't enter the war with abolition as a goal. But the South's fear of a rapidly growing and industrializing North and its need to protect slavery were very much the triggers for secession and for the opening of hostilities at Sumter. Most of the first half of 19th century American politics was distorted by the South's need to maintain parity with a rapidly growing North and Mid West in the House and Senate, i.e., Missouri Compromise, Bloody Kansas, etc.

I may be being obtuse, but the words that kept popping up were the number of “slave” states versus the number of “free” states.