Willamette River, OR

The Willamette River is a major tributary of the Columbia River. The river is 187 miles (301 km) long, lying entirely in northwestern Oregon in the United States. Flowing northward between the Oregon Coast Range and Cascade Range, the river and its tributaries form a basin called the Willamette Valley containing two-thirds of Oregon's population.

The Willamette rises in three separate forks in the mountains south and southeast of Eugene, at the southern end of the Willamette Valley. Formed by the confluence of its Middle and Coast forks near Springfield, the main stem meanders generally north for 187 miles (301 km) to the Columbia. The river's two most significant course deviations occur at Newberg, where it turns sharply east, and about 18 miles (29 km) downriver from Newberg, where it turns north again. Near its mouth north of downtown Portland the river splits into two channels that flow around Sauvie Island. The main channel enters the Columbia about 101 miles (163 km) from the larger stream's mouth on the Pacific Ocean, and the smaller Multnomah Channel enters the Columbia about 14.5 miles (23.3 km) further downstream near St. Helens in Columbia County.