Do you mean the American Civil War?
If so, then you should know that there was a long slow build-up over a few decades to this war. It culminated in Abe Lincoln being elected president, because he was against slavery. So the southern states had threatened to secede from the Union before that since they were against Lincoln, and this was all the end result of a long period of strife and tension.
There was also the Mason Dixon Line and the setting of always getting a Southern State that supported slavery along with a northern state that was against it, so that they kept the balance of power in Congress. Unfortunately, I don't think they had a slave state to go along with... Kansas I think it was, so they were protesting that.
Thus, it was like a volcano in that there were a number of events that raised the temperature of relations between the Slave and Free states that exploded when Lincoln was elected President back in 1861.
