The Copper River or Ahtna River (), Ahtna Athabascan ‘Atna’tuu (), "river of the Ahtnas", Tlingit Eeḵhéeni (), "river of copper", is a 290-mile (470 km) river in south-central Alaska in the United States. It drains a large region of the Wrangell Mountains and Chugach Mountains into the Gulf of Alaska. It is known for its extensive delta ecosystem, as well as for its prolific runs of wild salmon, which are among the most highly prized stocks in the world. The river is the tenth largest in the United States, as ranked by average discharge volume at its mouth. Description The Copper River rises out of the Copper Glacier, which lies on the northeast side of Mount Wrangell, in the Wrangell Mountains, within Wrangell-Saint Elias National Park. It begins by flowing almost due north in a valley that lies on the east side of Mount Sanford, and then turns west, forming the northwest edge of the Wrangell Mountains and separating them from the Mentasta Mountains to the northeast. It continues to turn southeast, through a wide marshy plain to Chitina, where it is joined from the southeast by the Chitina River (Ahtna Athabascan Tsedi Na' < tsedi "copper" + na’ "river"). The Copper River is approximately long. It drops an average of about , and drains more than —an area the size of West Virginia. The river runs at an average of . Downstream from its confluence with the Chitina it flows southwest, passing through a narrow glacier-lined gap in the Chugach Mountains within the Chugach National Forest east of Cordova Peak. There is an extensive area of linear sand dunes up to in height radiating from the mouth of the Copper River. Both Miles Glacier and Childs Glacier calve directly into the river. The Copper enters the Gulf of Alaska southeast of Cordova where it creates a delta nearly wide. History The name of the river comes from the abundant copper deposits along the upper river that were used by Alaska Native population and then later by settlers from the Russian Empire and the United States. Extraction of the copper resources was problematic due to navigation difficulties at the river's mouth. The construction of the Copper River and Northwestern Railway from Cordova through the upper river valley from 1908 to 1911 allowed widespread extraction of the mineral resources, in particular from the Kennecott Mine, discovered in 1898. The mine