A French cannon founder, Peyrembert, received permission to build a cannon factory here. Having gotten into difficulties, King Frederik V requested that his chancellery advisor, Johan Frederik Classen, take over the operation of the foundry. Under Classen's management the town blossomed, and there came a gunpowder mill, as well as light industry and handicrafts to the town. This resulted in Classen's being appointed Major General. On August 25, 1756 the king issued a document permitting Classen to call the town "Friederichswerk".
Classen was allowed to build a new foundry, Gjethuset, and it was constructed between 1761 and 1767. It has been used as a cannon foundry until 1928, and has been used for heavy industry until 1976. The building has been restored and reopened on June 12, 1996. It is now used as an art and culture center with theatre, music and art exhibitions. The original architect was either Laurids de Thurah or Nikolai Eigtved. The word Gjethus comes from Low German Gethus and means "foundry house".
Classen's home in the neoclassical style, Arresødal, is still standing. It is in private ownership, but can be viewed from the outside
