During the Meiji period, mine development was promoted under the policy of the Fengoku Robe (足尾銅山), and coal mining, Ashio Copper Mine, and Kamaishi Mine (釜石鉱山) with iron ore in Hokkaido and northern Kyushu were developed. The production of high-value gold and silver, even in small quantities, was at the top of the world. An important mine was the Ashio Copper Mine which existed since at least the 1600s. It was owned by the Tokugawa shogunate. At that time it produced about 1,500 tons annually. The mine was closed in 1800. In 1871 it became privately owned and reopened when Japan industrialized following the Meiji restoration. By 1885 it produced 4,090 tons of copper (39% of Japan's copper production). Due to a lack of regulations it caused substantial pollution. In 1911, the government passed the Factory Law which was Japan's first law to address industrial pollution. It was closed again in 1973.