The earliest known production of stoneware was in the Rhineland of Germany around 1280.[4] Initially, the process was used on earthenware. By the 15th century, small pottery towns of the Westerwald, including Höhr-Grenzhausen, Siegberg, Köln, and Raeren in Flanders, were producing a salt-glazed stoneware.[5] Westerwald Pottery was characterized by stamped medallions and the use of a cobalt oxide based colorant for decoration. Production of salt glaze pottery in Westerwald ceased because of environmental considerations in 1983.[6]