The Southern Aristocracy was very much operating on a pre-capitalist economy, with a system of pseudo-feudalism predominating in the slave economy. If the US Civil War was about capitalism, the northern industrialists, who benefitted from the Southern feudal economy keeping costs low, would have supported the South's war for slavery, not the North's attempts to end it.

Oh, say what is it called when someone is forced to work against their will for no money? I know there's a word for it...