Harper's Weekly engraving from 1869 showing Eli Whitney's (1765-1825) cotton gin in operation. The idea of interchangeable parts, made by such power-driven tools as this drill press, was not original with Whitney. In 1785 Jefferson visited a French inventor who was working on that principle; but Whitney was the first to translate a theory into a production system. In the South, the cotton gin revolutionized the way cotton was harvested and reinvigorated slavery.