The mechanization of spinning and weaving in England, between 1733 and 1785, greatly speeds up the industrial process and rapidly leads to a shortage of cotton. During most of the century the bulk of raw cotton arriving at Liverpool for the Lancashire mills is from India. The cotton grown in the southern states of America is commercially less viable because it is short-fibred.

The cotton fibres, which will be spun into cotton, have to be separated from the seeds which they protect and enmesh. This process, known as cotton picking, is done entirely by hand. The short fibres make it a slow and expensive task.

In 1793 Eli Whitney, a graduate of Yale, invents a machine which solves this problem. It consists of a hand-turned roller with projecting spikes. Each spike passes through a slot in a grid, wide enough to allow the spike to drag the cotton fibres through but too narrow for the cotton seeds to pass. They fall out into a separate container, while a revolving brush cleans the fibres, or lint, off the spikes.

Whitney's machine immediately trebles the speed at which cotton can be ginned, with major effects on the economy of the southern states of America. About forty times as much cotton (now established as 'king cotton') is produced in 1810 as in 1793. Vast new areas are taken in hand as plantations. The demand for slaves increases accordingly.