Copper Mountain is a 5,425-foot peak in the southeastern Olympic Mountains of Mason County, Washington, set on the boundary between two wilderness areas and between Olympic National Park and Olympic National Forest. Rising steeply above Lake Cushman near the Staircase Ranger Station, it has especially dramatic relief and sends water north to the Hamma Hamma River and south to the North Fork Skokomish River. Lieutenant Joseph P. O’Neil named it on July 7, 1890, after copper ore found there earlier that year, linking the mountain to a period of active non-Native exploration and mapping in the Olympic interior. Its geology reflects oceanic crust, sedimentary material, and later glaciation.