Make that Slave Based Agriculture, and I'll agree with you. The Midwest was agricultural too, but it was solidly on the side of the Union, even though many of its economic interests coincided with the South. The people in the midwest were willing to farm their own land, 40 acres at a time. The South was controlled totally by wealthy aristocrats who used slaves to work thousands of acres at a time. The aristrocrats never walked behind a plow.
That war was about economics only in the sense of protecting the slave industry. It was about a small group of wealthy and corrupt slavers attempting to protect and expand their evil institution. They were willing to break the Union and send hundreds of thousands of mostly poor white farmers to their deaths all for the purpose of protecting and expanding their wealth.