Goslar was founded in 922, and when in 968 the first silver was extracted from the metallic ore of the Rammelsberg, the city began to grow. It became one of the seats of the Holy Roman Empire until the 13th century. At the end of the 13th century Goslar became a member of the Hanseatic League, and prospered during the 15th and 16th centuries. The mines at the Rammelsberg, from where zinc, lead and copper were extracted, remained in operation until 1988.