Following drafting, and signing of the new United States Constitution, blacks in the country were completely disenfranchised, and most remained slaves. Slavery began to decline. Most northern states outlawed its practice shortly after the Revolution, and in the south, Tobacco, the primary cash crop, was losing value In 1794, Eli Whitney invented the cotton gin. This new invention helped to increase the profitability of cotton by mechanically removing its seeds. After 1800 the amount of cotton produced in the United States would double every 10 years. By the middle of the century, the United States produced three quarters of the worlds cotton.