The Elwha River drains a watershed of about 204,800 acres (82,880 ha) and flows generally north for 45 miles (72 km) from a perennial snowfield at an elevation of 4,763 feet (1,452 m) in the Olympic Mountains to Angeles Point at Freshwater Bay on the southern shore of the Strait of Juan de Fuca, about 33 miles (53 km) east-southeast of Clallam Bay and 6 miles (10 km) west-northwest of Port Angeles, Washington. Most of the river’s course lies within Olympic National Park. The Olympic Mountains primarily consist of accretionary wedge material, including sandstones, turbidites, and basaltic oceanic crust. During the Eocene epoch, approximately 56 to 34 million years ago, vents and fissures on the ocean floor of the Farallon Plate released lava that formed large underwater mountains and ranges known as seamounts. As the Farallon Plate was gradually subducted beneath the North America Plate, some of the seafloor rocks were scraped off and accreted to the continent. The nascent Olympic Mountains formed underwater and did not emerge above sea level until about 20 to 10 million years ago. During the Pleistocene epoch, a series of glacial advances sculpted the mountains. The Last Glacial Maximum occurred during the Fraser Glaciation, when the vast Cordilleran Ice Sheet descended from the north. As the ice sheet advanced, it encountered the Olympic Mountains and split into the Juan de Fuca and Puget ice lobes. These lobes carved out the current waterways and advanced as far south as present-day Olympia. Ice flowed up river valleys to an elevation of 3,800 feet (1,200 meters). When the ice retreated, sediments from Vancouver Island and the Canadian Coast Ranges were deposited and subsequently buried by alluvial sediments originating from the Olympic Mountains.

The Klallam Tribe historically lived in villages on both sides of the Strait of Juan de Fuca. On the Olympic Peninsula, their villages included Hoko, Clallam Bay, Pysht, Deep Creek, Freshwater Bay, the Elwha Valley and river mouth, the shores of Port Angeles, and creeks farther east. On the north side of the strait, near Victoria, was the Klallam village of Beecher Bay. The Lower Elwha Klallam historically occupied several villages along the Elwha River and on Freshwater Bay. The Elwha Klallam have a creation story centered on a rock along the river, where the Creator would scoop dirt from pits and hollows in the rock to form humans. According to oral tradition, the Elwha River is home to Thunderbird, an important symbol of strength for the Klallam people. Thunderbird lived in a cave and chased the salmon upriver, sending thunder and lightning toward the mouth of the Elwha, where the Klallam caught the fish. In 1855, the Lower Elwha Klallam Tribe was recognized by the United States in the Point No Point Treaty. However, the Klallam refused to move onto the Skokomish Reservation on Hood Canal and remained in their traditional villages. Settlers began arriving in the lower Elwha Valley in the 1860s, pushing many Klallam people from their traditional homesites. In the late 18th and 19th centuries, the tribe suffered high fatalities from infectious European diseases such as smallpox and measles. In the 20th century, the federal government persuaded the tribe to relocate from their village at Port Angeles to allow for the industrial development of lumber and paper mills along the waterfront. In 1968, the land at the mouth of the Elwha River was designated as the Lower Elwha Reservation. It includes about 1,000 acres (405 hectares) of land on and near the Elwha River. Salmon have always been an important seasonal subsistence food for the Elwha Klallam. The river provides a spawning habitat for Chinook, coho, chum, sockeye, and pink salmon, as well as steelhead, coastal cutthroat, bull trout, and Dolly Varden char.

In 1910, the Elwha Dam was built about four miles (6 km) upstream from the river mouth under the direction of Thomas Aldwell, who had previously bought tracts of land around the river. Aldwell and his contractors cut corners during construction, including illegally omitting fish passages and failing to secure the structure to the bedrock. In 1912, as the reservoir began filling, the lower sections of the dam gave way, and a torrent of water flooded the Lower Elwha Reservation. The dam was reconstructed and completed in 1913, creating a reservoir known as Lake Aldwell. The Elwha River Hydroelectric Power Plant historic district comprised 3.5 acres (1.4 hectares), including the dam, powerhouse, five penstocks, and the surge tank. In 1926, the Glines Canyon Dam was completed about seven miles (11 km) upstream from the Elwha Dam, impounding Lake Mills. These projects helped fuel economic growth and development on the Olympic Peninsula and in the community of Port Angeles. Before the dams were built, approximately 400,000 adult salmon returned annually to spawn in 70 miles (110 km) of river habitat. By 2014, fewer than 4,000 salmon returned each year in just 4.9 miles (7.9 km) of remaining spawning habitat. By 2010, the combined power output of both dams provided only 38% of the electricity needed to operate one sawmill. In 2011, the National Park Service removed the two dams as part of the $325 million Elwha Ecosystem Restoration Project. The sediment release created 70 acres (28 hectares) of estuary habitat on the Strait of Juan de Fuca. While the dams had a major impact on the Elwha River, other human activities have significantly degraded the health of the lower floodplain. Restoration efforts also include removing abandoned dikes and constructing engineered logjams to allow the river to form side channels and reconnect to its floodplain. The lower floodplain is being reforested with native species, and exotic plants are being eradicated. Additional actions have been identified in the middle and lower portions of the river, as well as in the estuary and nearshore habitat, to further accelerate watershed recovery. Read more here and here. Explore more of the Elwha River and Angeles Point here: