Final answer:
Eli Whitney's invention was the cotton gin, which revolutionized the cotton industry and had a major impact on slavery.
Step-by-step explanation:
Eli Whitney's invention was the cotton gin, which he patented in 1794. The cotton gin revolutionized the cotton industry by significantly speeding up the process of separating cotton fibers from the seeds. This invention had a major impact on slavery because it increased the demand for cotton and therefore the need for enslaved labor to cultivate and harvest the crop. The cotton gin made cotton production more profitable, which in turn led to the expansion and perpetuation of slavery in the American South.