Eli Whitney was an inventor of both the cotton gin and the mass production particularly of muskets.
Eli Whitney invented the cotton gin to reduce the number of slaves necessary to process cotton. The cotton gin made it possible to profitably grow short staple cotton. Previously only long stable could be profitably grown because of the difficulty of separating the cotton fibers from the seeds. With the cotton gin it was profitable to separate the fibers of short staple cotton which could be grown throughout the south, while long stable cotton could only be grown in costal regions of six southern states.
Instead of the invention of the cotton gin reducing the number of slaves it greatly magnified the number of slaves. Plantations sprang up all over the south that needed slaves.
Eli Whitney made very little money on his invention of the cotton gin while it made the south fabulously wealthy.
Eli also invented the interchangeable parts and mass production of muskets. The manufacturing power of the north based on Eli Whitney's invention of mass production greatly aided in the defeat of the south during the Civil War.