If you ask a Southerner, they'll claim it was the War of Northern Aggression, as they'll claim the North started it first. Actually, the first shot fired at Fort Sumter was from a Southern gun. The South started it.
The south because they started the brawl at fort sumter. Abraham Lincoln was trying to restock the fort. He left the south with two decisions: either to attack the supply ship, which had happened before, therefore making them draw blood first; or to let the ship go and to look weak. The south ended up attacking the fort before the northern ship got to it, therefore starting the war. The fort was, however, mostly empty, as the critical thinker Abraham Lincoln expected this.
It's the same argument that people have about Japan & the USA in WWII. Some would say that the USA forced Japan into attacking Pearl Harbor by choking off their resources. I say whoever flinches first - they caused it.