I believe this is referring to the Civil War, in which case the southern states were Confederate and the northern states were Union. They both had different views on slavery, that was the main reason. The southern states felt used leading up to the war because they provided food and crops for the northern states and still weren't considered as industrious or important, really. When laws on slavery became strict, that was the last straw for southern states, as slaves were the main reason they could keep their crops running- plus they were cheap. It was the last straw from them, and they ended up separating from the Union because if it.