That would be the Columbia River. This river separates approximately two thirds of southern Washington from northern Oregon. At a place on the 46th parallel north this river total enters the state of Washington, and this parallel becomes the border line that separates the two states.
The Columbia River
The Columbia River separates Washington and Oregon. It runs from British Columbia, Canada, through Washington state, and forms part of the border between Washington and Oregon before emptying into the Pacific Ocean.
The Columbia River
The Columbia River separates Washington State and Oregon.
There are many rivers that create state boundaries in the United States. The river that separates Washington from Oregon is the Columbia River.
The Pacific Ocean, Canada, Idaho, and the Columbia River separates us from Oregon
Washington and Oregon border the Columbia River.
The lake that separates Washington and Oregon is the Columbia River. While it is primarily a river, it forms a natural boundary between the two states and has several large reservoirs along its course, such as Lake Bonneville. However, there is no single lake that distinctly serves as the border between the two states. The Columbia River is crucial for navigation, hydropower, and recreation in the region.
If you mean Oregon and Washington, you'd be looking for the Columbia River...
Cascades
The state to the north of California is Oregon. Oregon is bordered to the north by the Columbia River, which separates it from Washington. Additionally, the Pacific Ocean lies to the west of Oregon.
The Columbia River.