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.