Invented by Eli Whitney in 1793, it is used to separate cotton fiber from its seeds. Prior to the invention of the cotton gin, removing the seeds from the fiber was done by hand, a very tedious and expensive process.

The cotton gin uses teeth attached to a cylinder which are rotated through a set of fixed teeth. Cotton fed to cylinder is caught on the teeth and pulled through the fixed teeth which are spaced too close together to allow the seeds to also pass through.

Also called a saw gin, it is one of the most important factors in the creation of the enormous US cotton industry.