Before the Civil War, the northern economy was rapidly industrializing. Do not think of the North as industrialized during the war, they were still primarily agricultural, but were moving closer to industrialization. The difference was the South was not industrializing at all. The South was becoming extremely wealthy, but they put all their wealth back into slavery and their land. Southerners may have been wealthy, but they were cash poor. With no liquid money, there was nothing to invest in new technologies and industry. Not to mention there was no motivation to with the amount of money they made from cotton.
Historically Speaking 