<P> While Whitney's gin facilitated the cleaning of seeds from short - staple cotton, it damaged the fibers of (extra-long staple) cotton (Gossypium barbadense). In 1840 Fones McCarthy received a patent for a "Smooth Cylinder Cotton - gin", a roller gin . McCarthy's gin was marketed for use with both short - staple and extra-long staple cotton, but was particularly useful for processing long - staple cotton . After McCarthy's patent expired in 1861, McCarthy type gins were manufactured in Britain and sold around the world . McCarthy's gin was adopted for cleaning the Sea Island variety of extra-long staple cotton grown in Florida, Georgia and South Carolina . It cleaned cotton several times faster than the older gins, and, when powered by one horse, produced 150 to 200 pounds of lint a day . The McCarthy gin used a reciprocating knife to detach seed from the lint . Vibration caused by the reciprocating motion limited the speed at which the gin could operate . In the middle of the 20th Century gins using a rotating blade replaced ones using a reciprocating blade . These descendants of the McCarthy gin are the only gins now used for extra-long staple cotton in the United States . </P> <P> Prior to the introduction of the mechanical cotton gin, cotton had required considerable labor to clean and separate the fibers from the seeds . With Eli Whitney's gin, cotton became a tremendously profitable business, creating many fortunes in the Antebellum South . Cities such as New Orleans, Louisiana; Mobile, Alabama; Charleston, South Carolina; and Galveston, Texas became major shipping ports, deriving substantial economic benefit from cotton raised throughout the South . Additionally, the greatly expanded supply of cotton created strong demand for textile machinery and improved machine designs that replaced wooden parts with metal . This led to the invention of many machine tools in the early 19th century . </P> <P> The invention of the cotton gin caused massive growth in the production of cotton in the United States, concentrated mostly in the South . Cotton production expanded from 750,000 bales in 1830 to 2.85 million bales in 1850 . As a result, the region became even more dependent on plantations and slavery, with plantation agriculture becoming the largest sector of its economy . While it took a single slave about ten hours to separate a single pound of fiber from the seeds, a team of two or three slaves using a cotton gin could produce around fifty pounds of cotton in just one day . The number of slaves rose in concert with the increase in cotton production, increasing from around 700,000 in 1790 to around 3.2 million in 1850 . By 1860, black slave labor from the American South was providing two - thirds of the world's supply of cotton, and up to 80% of the crucial British market . The cotton gin thus "transformed cotton as a crop and the American South into the globe's first agricultural powerhouse". </P> <P> Because of its inadvertent effect on American slavery, and on its ensuring that the South's economy developed in the direction of plantation - based agriculture (while encouraging the growth of the textile industry elsewhere, such as in the North), the invention of the cotton gin is frequently cited as one of the indirect causes of the American Civil War . </P>

How much of the world's supply of cotton came from the south