Answer:
While it was true that the cotton gin reduced the labor of removing seeds, it did not reduce the need for slaves to grow and pick the cotton. In fact, the opposite occurred. Cotton growing became so profitable for the planters that it greatly increased their demand for both land and slave labor.
Cotton transformed the United States, making fertile land in the Deep South, from Georgia to Texas, extraordinarily valuable. Growing more cotton meant an increased demand for slaves. Slaves in the Upper South became incredibly more valuable as commodities because of this demand for them in the Deep South.
North, stated that cotton “was the most important proximate cause of expansion” in the 19th century American economy. Cotton accounted for over half of all American exports during the first half of the 19th century. The cotton market supported America's ability to borrow money from abroad.
The gin improved the separation of the seeds and fibers but the cotton still needed to be picked by hand. The demand for cotton roughly doubled each decade following Whitney's invention. So cotton became a very profitable crop that also demanded a growing slave-labor force to harvest it.
