The river is one of the few in the Pacific Northwest with all five species of native Pacific salmon (chinook, coho, chum, sockeye, and pink salmon), plus four anadromous trout species (steelhead,coastal cutthroat trout, bull trout, and Dolly Varden char). From 1911 to 2014, dams blocked fish passage on the lower Elwha River. Before the dams, 400,000 adult salmon returned yearly to spawn in 70 miles (110 km) of river habitat. Prior to dam removal, fewer than 4,000 salmon returned each year in only 4.9 miles (7.9 km) of habitat below the lower dam. The National Park Service removed the two dams as part of the $325 million Elwha Ecosystem Restoration Project. Dam removal work began in September 2011 and was completed in August 2014. The river has already carried sediment to its mouth, creating 70 acres of estuary habitat at the Strait of Juan de Fuca.
The first documented use of the name Elwha River dates to Henry Kellett's 1846 map.
The river source is in Jefferson County at the Elwha Snowfinger. The Elwha Snowfinger is located near Dodwell Dixon Pass at an elevation of 4,763 feet. The snowfield is created by continous winter and spring avalanches into the upper pass area.