There were at least three economic factors that played a part in establishing African slavery in the United States: the need for a large number of laborers to work plantations, the tariff policy that increased the price of manufactured goods, and the agricultural nature of the South's economy. Plantations required a much larger number of workers than could be supplied locally, and slaves were imported to fulfill that need. The maintenance of slaves did incur cost, but not as much as if they were paid a standard wage. The tariff policy was a main driver for keeping the South agricultural as opposed to industrial. While the North was in the midst of industrialization, the South stayed with agriculture to avoid having to pay the high tariffs on imported goods which would have been necessary to support industry. Finally, the agricultural economy itself promoted slavery, because by not demanding tariffs, the South was totally dependent on agriculture to meet its needs. Slave labor enabled the South to survive in an increasingly industrialized world, but there was no manpower left for industry even if the South had been amenable to it. (1918).
The impact of slavery on the United States as an emerging nation was to polarize the North and the South into vastly different cultures, one industrialized and moving forward with technology, the other tied to agriculture and languishing in the past. In the end, this polarization led to the Civil War.
Phillips, U.B. (1918). Chapter XVIII Economic Views Of Slavery: A Survey Of The Literature. In American Negro Slavery: A Survey of the Supply, Employment and Control of Negro Labor as Determined by the Plantation Regime. (pp. 344-358). New York: D. Appleton. Retrieved on May 25, 2005 at: http://www.questia.com/PM.qst?a=o&d=54792852