 Annual copper production from the mines peaked in 1906 at 100 million pounds (45,000 metric tons), then declined to 67 million pounds (30,000 metric tons) by 1912 in response to lower prices.Output dropped to 46 million pounds (21,000 metric tons) of refined copper in the strike year of 1913, but rebounded due to high copper prices during World War I to 77 million pounds (35,000 metric tons) in 1917.The boost in production was attained partly by purchase of the Tamarack Mining Company in 1917.