About 1,240 miles · WA, OR · source Columbia Lake, BC · mouth Pacific at Astoria
Columbia River map
The Columbia flows about 1,240 miles from British Columbia through Washington to the Pacific, forming about 300 miles of the Washington–Oregon border. It carries more water to the Pacific than any other river in the Americas.
Where the Columbia is
The Columbia rises at Columbia Lake in the Rocky Mountain Trench of British Columbia, loops north and then south, and enters the US in northeastern Washington as Lake Roosevelt, the reservoir behind Grand Coulee Dam. It swings around the Big Bend of central Washington, receives the Snake near Pasco, and from there flows west as the border with Oregon, cutting through the Cascade Range in the Columbia River Gorge and reaching the Pacific between Astoria, Oregon, and Ilwaco, Washington. About 745 of its roughly 1,240 miles are in the United States.
States along the river
- Washington — about 450 miles wholly inside the state, then the southern border.
- Oregon — the northern border from Wallula Gap to the sea, about 300 miles.
The basin is far wider than the river: the Snake drains Idaho, western Wyoming and eastern Oregon, and other tributaries reach into Montana, Nevada and Utah. In all, the Columbia system drains about 258,000 square miles in seven states and British Columbia.
Key measurements
- Length: about 1,240 miles; the largest river by volume flowing into the Pacific from North America.
- Main tributaries: the Snake (about 1,080 miles), the Willamette (joins at Portland), the Spokane, Yakima, Deschutes, Kootenay and Pend Oreille.
- Fourteen dams on the US and Canadian mainstem. Grand Coulee (1942) is the largest power station in the US; Bonneville (1938) is the lowest dam, 40 miles east of Portland. Only the last 145 miles run free.
- Ocean-going ships reach Portland and Vancouver; barges reach Lewiston, Idaho, 465 miles inland, through eight locks.
Cities on the river
Portland, Oregon, the largest city in the basin, sits on the Willamette a few miles above its confluence with the Columbia; Vancouver, Washington, faces it across the main river. Upstream are the Tri-Cities of Kennewick, Pasco and Richland at the Snake and Yakima confluences, Wenatchee, and the Hanford nuclear site. Astoria, at the mouth, was founded in 1811 as the first US settlement on the Pacific coast. Seattle is about 100 miles north of the river.
How the river shaped the map
Lewis and Clark reached the Pacific down the Columbia in 1805, and the river was the US claim to the Oregon Country. When Washington Territory was split from Oregon in 1853, the river was the natural dividing line from the Cascades to the sea; east of Wallula Gap the border jumps to the 46th parallel. The Gorge is the only near-sea-level route through the Cascades, which is why Interstate 84 and the railroads follow it.
Related maps
- Snake River — the largest tributary.
- Cascade Range — the mountains the river cuts through.
- Pacific Northwest states.
- Longest US rivers · All geography maps.