Howe Sound Company's Holden Mine was one of the largest copper mines in the United States during its productive life, from 1938 to 1957. The mine and mill facilities produced approximately 212 million pounds of copper, 40 million pounds of zinc, 2 million ounces of silver, and 600 thousand ounces of gold from approximately 10 million tons of ore. During the operation, about 57 miles of underground workings were excavated. About 8.5 million tons of mill tailings, which consist of the ground rock remaining after minerals with economic values were removed, were placed on National Forest System lands near Railroad Creek, covering approximately 90 acres. Another 1.5 million tons of tailings were put back into the mine.