Columbia River

The Columbia River (Upper Chinook: Wimahl or Wimal; Sahaptin: Nch’i-Wàna or Nchi wana; Sinixt dialect swah'netk'qhu) is the largest river in the Pacific Northwest region of North America. The river forms in the Rocky Mountains of British Columbia, Canada. It flows northwest and then south into the U.S. state of Washington, then turns west to form most of the border between Washington and the state of Oregon before emptying into the Pacific Ocean. The river is 1,243 mi (2,000 km) long, and its largest tributary is the Snake River. Its drainage basin is roughly the size of France and extends into seven states of the United States and one Canadian province. The fourth-largest river in the United States by flow, the Columbia has the greatest flow of any river into the eastern Pacific.

The Columbia and its tributaries have been central to the region's culture and economy for thousands of years. They have been used for transportation since ancient times, linking the region's many cultural groups. The river system hosts many species of anadromous fish, which migrate between freshwater habitats and the saline waters of the Pacific Ocean. These fish—especially the salmon species—provided the core subsistence for native peoples.

The first documented European discovery of the Columbia River occurred when Spanish explorer Bruno de Heceta sighted the river's mouth in 1775. On May 11, 1792, a private American ship, Columbia Rediviva, under Captain Robert Gray from Boston became the first non-indigenous vessel to enter the river. Later in 1792, William Robert Broughton of the British Royal Navy commanding HMS Chatham as part of the Vancouver Expedition, navigated past the Oregon Coast Range and 100 miles (160 km) upriver to what is now Vancouver, Washington. In the following decades, fur-trading companies used the Columbia as a key transportation route. Overland explorers entered the Willamette Valley through the scenic but treacherous Columbia River Gorge, and pioneers began to settle the valley in increasing numbers. Steamships along the river linked communities and facilitated trade; the arrival of railroads in the late 19th century, many running along the river, supplemented these links.

Since the late 19th century, public and private sectors have extensively developed the river. To aid ship and barge navigation, locks have been built along the lower Columbia and its tributaries, and dredging has opened, maintained, and enlarged shipping channels. Since the early 20th century, dams have been built across the river for power generation, navigation, irrigation, and flood control. The 14 hydroelectric dams on the Columbia's main stem and many more on its tributaries produce more than 44 percent of total U.S. hydroelectric generation. Production of nuclear power has taken place at two sites along the river. Plutonium for nuclear weapons was produced for decades at the Hanford Site, which is now the most contaminated nuclear site in the United States. These developments have greatly altered river environments in the watershed, mainly through industrial pollution and barriers to fish migration.

The Columbia begins its 1,243 mi (2,000 km) journey in the southern Rocky Mountain Trench in British Columbia (BC). Columbia Lake –  2,690 ft (820 m) above sea level –  and the adjoining Columbia Wetlands form the river's headwaters. The trench is a broad, deep, and long glacial valley between the Canadian Rockies and the Columbia Mountains in BC. For its first 200 mi (320 km), the Columbia flows northwest along the trench through Windermere Lake and the town of Invermere, a region known in BC as the Columbia Valley, then northwest to Golden and into Kinbasket Lake. Rounding the northern end of the Selkirk Mountains, the river turns sharply south through a region known as the Big Bend Country, passing through Revelstoke Lake and the Arrow Lakes. Revelstoke, the Big Bend, and the Columbia Valley combined are referred to in BC parlance as the Columbia Country. Below the Arrow Lakes, the Columbia passes the cities of Castlegar, located at the Columbia's confluence with the Kootenay River, and Trail, two major population centers of the West Kootenay region. The Pend Oreille River joins the Columbia about 2 miles (3 km) north of the United States–Canada border.

The Columbia enters eastern Washington flowing south and turning to the west at the Spokane River confluence. It marks the southern and eastern borders of the Colville Indian Reservation and the western border of the Spokane Indian Reservation. The river turns south after the Okanogan River confluence, then southeasterly near the confluence with the Wenatchee River in central Washington. This C-shaped segment of the river is also known as the "Big Bend". During the Missoula Floods 10–15,000 years ago, much of the floodwater took a more direct route south, forming the ancient river bed known as the Grand Coulee. After the floods, the river found its present course, and the Grand Coulee was left dry. The construction of the Grand Coulee Dam in the mid-20th century impounded the river, forming Lake Roosevelt, from which water was pumped into the dry coulee, forming the reservoir of Banks Lake.

The river flows past The Gorge Amphitheatre, a prominent concert venue in the Northwest, then through Priest Rapids Dam, and then through the Hanford Nuclear Reservation. Entirely within the reservation is Hanford Reach, the only U.S. stretch of the river that is completely free-flowing, unimpeded by dams, and not a tidal estuary. The Snake River and Yakima River join the Columbia in the Tri-Cities population center. The Columbia makes a sharp bend to the west at the Washington–Oregon border. The river defines that border for the final 309 mi (497 km) of its journey.

The Deschutes River joins the Columbia near The Dalles. Between The Dalles and Portland, the river cuts through the Cascade Range, forming the dramatic Columbia River Gorge. Via the gorge, the Columbia crosses the Cascades at a lower elevation than any other river. The gorge is known for its strong and steady winds, scenery, and its role as a transportation link. The river continues west, bending sharply to the north-northwest near Portland and Vancouver, Washington, at the Willamette River confluence. Here the river slows considerably, dropping sediment that might otherwise form a river delta at the Columbia's mouth. Near Longview, Washington and the Cowlitz River confluence, the river turns west again. The Columbia empties into the Pacific Ocean just west of Astoria, Oregon, over the Columbia Bar, a shifting sandbar that makes the river's mouth one of the most hazardous stretches of water to navigate in the world. Because of the danger and the many shipwrecks near the mouth, it acquired a reputation as the "Graveyard of Ships".