Largest tributaries
The Columbia River Estuary is situated on the Oregon–Washington border and the Pacific Coast of the United States. It was traditionally inhabited by the Chinook Native Americans and discovered by settlers in 1788. The Estuary plays host to a plethora of species of marine and terrestrial flora and fauna, and multiple conservation organisations exist that maintain the area. Geologically, it is situated on a continental margin of the North American Plate.
Geographically, the Estuary of the Columbia River is defined as extending inland as far as the Bonneville Dam. It is the furthest point at which fluctuation of free-flowing water levels based on tide is substantial enough to be recorded.
