The war of Northern Aggression was over states rights. When Abraham Lincoln was elected in 1860 with no electoral votes at all from below the Mason Dixon Line, the South decided that time had come to break the links with the rest of the Union The action was not shocking, as secession had been threatened for years, but the actual break must have sobered many who had never before faced the reality of separation. By February, 1861, seven states had seceded, and following the firing on Ft. Sumter, South Carolina and Lincoln’s subsequent call for 75,000 volunteers to put down the rebellion, four more states left.

The question is really asking for the causes of the Civil War.

The information is below

Here is a link that will help:

http://en.wikipedia.org/wiki/Confederate_States_of_America

Very simple answer? Slavery.