Eli Whitney was born on December 8, 1765, in Westborough, Massachusetts. Growing up, Whitney, whose father was a farmer, proved to be a talented mechanic and inventor. Among the objects he designed and built as a youth were a nail forge and a violin. In 1792, after graduating from Yale College (now Yale University), Whitney headed to the South. He originally planned to work as a private tutor but instead accepted an invitation to stay with Catherine Greene (1755–1814), the widow of American Revolutionary War (1775-83) general Nathanael Greene, on her plantation, known as Mulberry Grove, near Savannah, Georgia. While there, Whitney learned about cotton production–in particular, the difficulty cotton farmers faced making a living.

In many ways, cotton was an ideal crop; it was easily grown, and unlike food crops its fibers could be stored for long periods of time. But cotton plants contained seeds that were difficult to separate from the soft fibers. A type of cotton known as long staple was easy to clean, but grew well only along coastal areas. The vast majority of cotton farmers were forced to grow the more labor-intensive short-staple cotton, which had to be cleaned painstakingly by hand, one plant at a time. The average cotton picker could remove the seeds from only about one pound of short-staple cotton per day.

Greene and her plantation manager, Phineas Miller (1764-1803), explained the problem with short-staple cotton to Whitney, and soon thereafter he built a machine that could effectively and efficiently remove the seeds from cotton plants. The invention, called the cotton gin (“gin” was derived from “engine”), worked something like a strainer or sieve: Cotton was run through a wooden drum embedded with a series of hooks that caught the fibers and dragged them through a mesh. The mesh was too fine to let the seeds through but the hooks pulled the cotton fibers through with ease. Smaller gins could be cranked by hand; larger ones could be powered by a horse and, later, by a steam engine. Whitney’s hand-cranked machine could remove the seeds from 50 pounds of cotton in a single day. Whitney wrote to his father: "One man and a horse will do more than fifty men with the old machines…Tis generally said by those who know anything about it, that I shall make a Fortune by it."

Whitney received a patent for his invention in 1794; he and Miller then formed a cotton gin manufacturing company. The two entrepreneurs planned to build cotton gins and install them on plantations throughout the South, taking as payment a portion of all the cotton produced by each plantation. While farmers were delighted with the idea of a machine that could boost cotton production so dramatically, they had no intention of sharing a significant percentage of their profits with Whitney and Miller. Instead, the design for the cotton gin was pirated and plantation owners constructed their own machines–many of them an improvement over Whitney’s original model.

The patent laws of the time had loopholes that made it difficult for Whitney to protect his rights as an inventor. Even though the laws were changed a few years later, Whitney’s patent expired before he ever realized much profit. Still, the cotton gin had transformed the American economy. For the South, it meant that cotton could be produced plentifully and cheaply for domestic use and for export, and by the mid-19th century, cotton was America’s leading export. For the North, especially New England, cotton’s rise meant a steady supply of raw materials for its textile mills.

One inadvertent result of the cotton gin’s success, however, was that it helped strengthen slavery in the South. Although the cotton gin made cotton processing less labor-intensive, it helped planters earn greater profits, prompting them to grow larger crops, which in turn required more people. Because slavery was the cheapest form of labor, cotton farmers simply acquired more slaves.

Patent-law issues prevented Whitney from ever significantly profiting from the cotton gin; however, in 1798, he secured a contract from the U.S. government to produce 10,000 muskets in two years, an amount that had never been manufactured in such a short period. Whitney promoted the idea of interchangeable parts: standardized, identical parts that would make for faster assembly as well as easier repair of various objects and machines. At the time, guns were typically built individually by skilled craftsmen, so that each finished device was unique. Although it ultimately took Whitney some 10 years, instead of two, to fulfill his contract, he was credited with playing a pioneering role in the development of the American system of mass-production.

In 1817, Whitney, then in his early 50s, married Henrietta Edwards, with whom he would have four children. He died on January 8, 1825, at age 59.