Civil war was fought over the moral issue of slavery. In fact, it was the economics of slavery and political control of that was central to the conflict. A key issue was states right. The southern states wanted to assert their authority over the federal government so they could abolish federal laws interfering with the Souths right to keep slaves and take them wherever they wished.
Another factor was territorial expansion. The South wished
to take slavery into the western territories, while the North was commited to keeping them open to white labour alone. Meanwhile the newly formed Republican party, whose members were strongly opposed to the west ward expansion of slavery into news state was gaining prominence.
The election of a Republican, Abraham Lincoln, as president in 1860 sealed the deal. His victory with a single southern electoral vote was a clear signal to the Southern states that they had lost all influence.