The "cause of the war" was that Lincoln did not accept the legal Secession of any of the Southern States. It upset the apple cart. The cause of Secession was the desire of the citizens of Southern states to leave the USA and form a more perfect union. I may be a little partial, but I believe the Texas Ordinance of Secession is an eloquent explanation of the riff between the Centralists and States Rights supporters.
http://lsjunction.com/docs/secesson.htm