The town was founded in 1226 by count Adolf I of Mark. The name Hamm means "corner" in the old Low German dialect, that was spoken in that time. This name may have been given due to the location of Hamm in the corner of the Lippe river and the narrow Ahse affluent.
In 1469 Hamm became a member of the Hanseatic League. It was one of the most powerful towns in the region, while the large cities of the today's Ruhr area were only tiny villages. In the 19th century coal mining and steel production became important in Hamm, just as in the adjoining Ruhr area.