Whitney's cotton gin model was capable of cleaning 50 pounds (23 kg) of lint per day. The model consisted of a wooden cylinder surrounded by rows of slender spikes, which pulled the lint through the bars of a comb-like grid. The grids were closely spaced, preventing the seeds from passing through. Loose cotton was brushed off, preventing the mechanism from jamming.

　　Many contemporary inventors attempted to develop a design that would process short staple cotton, and Hodgen Holmes, Robert Watkins, William Longstreet, and John Murray had all been issued patents for improvements to the cotton gin by 1796. However, the evidence indicates Whitney did invent the saw gin, for which he is famous. Although he spent many years in court attempting to enforce his patent against planters who made unauthorized copies, a change in patent law ultimately made his claim legally enforceable – too late for him to make much money from the device in the single year remaining before the patent expired.

　　Effects in the United States

　　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 introduction of "teeth" in his cotton gin to comb out the cotton and separate the seeds, 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.

　　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, and – according to many historians – was the start of the Industrial Revolution".

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