The cotton gin is a machine that is used to pull cotton fibers from the cotton seed. Eli Whitney invented the cotton gin in 1793 or 1794. At that time, Whitney was in the employ of Catherine Greene, the widow of General Nathaniel Greene. While there are claims that similar machines had been invented prior to Whitney’s gin, there is no firm evidence to support such claims. Whitney was thus granted a patent on March 14th, 1794, for his "new and useful improvement in the mode of Ginning cotton."
The invention of the cotton gin caused a revolution in the production of cotton in the southern United States, and had an enormous impact on the institution of slavery in this country. Before the invention of the cotton gin, not only was the raising of cotton very labor intensive, but separating the fiber from the cotton seed itself was even more labor intensive. Only the largest plantations found raising cotton cost effective. The invention of the cotton gin and its manufacture changed that. Growing and cultivating cotton became a lucrative and less labor-intensive cash crop, contributing immensely to the rise of cotton production in the Deep South. This, in turn, led to an increase in the number of slaves and slaveholders, and to the growth of a cotton-based agricultural economy in the South.
While it cannot be stated with certainty that the invention of the cotton gin saved and sustained slavery in the United States, it certainly was a major factor in the spread of slavery into Georgia, Alabama, and Mississippi.