You still have to wonder why the south never built factories to compete with the north. They exported most of their cotton to the north just to buy it back again the the form of textiles, so slavery working by hand wasn't able to compete with factories on that level.

I'd venture that the north's earlier industrialization built up experience and supporting infrastructure which made it a dubious business prospect for any southerner that might have considered building a factory, along with the fact that making textiles by manpower alone made less money than picking cotton and exporting it.