I would make the argument that slavery was essential to the national economy in exploring the production of cotton in the South. The advent of the cotton gin helped to make cotton production easier. The separation of seeds from cotton and the ability to process cotton for factories in the North and abroad helped to make the Southern part of the United States "the cotton kingdom." Slavery was essential in this process. As cotton production increased, more slaves were needed to pick more cotton, thereby making more profit and enabling more slaves to be purchased. The rise in cotton production accompanied the rise in slavery. Seeing that cotton was able to be freely traded for profit in both the North and in Europe, the economic condition of the nation increased. The South's product benefited the North and enabled trade abroad, helping to make the national economy a great power on the world stage.
Not merely in cotton, but in general, slavery propped the economy of the South. In the agrarian tradition of the South, slaves became part of the ability to generate wealth and make the South economically formidable. Just as the factory workers in the North made unlimited profit for the factory owners, the Southern slave made huge profits for the plantation owners. The ability to use slave labor for wealth enabled production of goods and crops to beget more slave labor for greater wealth. Southern economic expansion became dependent on slavery. This economic growth enabled the nation to become wealthier and more visible in the world economic order. Slavery became a way in which the Southern part of the United States was able to generate economic power. The fact that Southern economic wealth was contingent on trade with the North and worldwide partners helped to enhance American overall economic wealth to a prominent space on the world stage.