Explain why the south was generally excluded from industrial development and fell into a "third world" economic dependency.

Kind of a tough question to answer. Basically, the south was extremely fertile and created massive amounts of tobacco and cotton pre-civil war. So they needed a lot of land to make these farms. The north had densely populated cities and the south needed a place to turn raw materials like cotton, into processed materials like fabrics. So the North became massively industrialized because of the south. Hopefully that makes sense.