How it began
Eli Whitney, a recent Yale graduate from Massachusetts, went south in 1792 to take a job as a private tutor on a plantation in Georgia. His employer, the plantation owner Catherine Greene, encouraged him to find a way to clean cotton and gave him a secret workshop, where he worked through the winter and spring. He received a patent in 1794. The National Archives notes that his idea was based on earlier gins and on ideas from other people, including Greene and enslaved laborers, and that some regard these as the rightful inventors.
Before it existed
Southern planters wanted a profitable crop at a time when tobacco was declining because of over-supply and soil exhaustion. Long-staple cotton, which was easy to separate from its seeds, could be grown only along the coast. The one variety that grew inland had sticky green seeds that were time-consuming to pick out of the cotton bolls by hand.
How it works
The gin mechanized the removal of seeds from cotton fiber. A small gin could be cranked by hand, and larger versions could be harnessed to a horse or driven by water power. Whitney wrote to his father that "one man and a horse will do more than fifty men with the old machines."
Who pushed back
Whitney and his partner Phineas Miller first tried to install gins across the South and charge farmers two-fifths of the profit, paid in cotton. Farmers resented this as an exorbitant tax and built their own versions, claiming them as new inventions. Because of a loophole in the 1793 patent act, the partners could not win an infringement suit until the law was changed in 1800. South Carolina agreed to buy the patent right for 50,000 dollars in 1802.
What changed first
After the invention, the yield of raw cotton doubled each decade after 1800. Demand was fed by machines to spin and weave cotton and by the steamboat to carry it. By 1850 America was growing three-quarters of the world's supply of cotton, and by the middle of the century the South provided three-fifths of American exports, most of it cotton.
What lasted
The National Archives calls the growth of slavery the most significant effect. The gin reduced the labor of removing seeds but not of growing and picking, and cotton became so profitable that demand for land and enslaved labor rose sharply. There were six slave states in 1790 and 15 in 1860, by which time about one in three Southerners was enslaved.
