name a river that forms a border between the states of washinghton and oregon? which river forms a border between the states of washington and oregon? name the river that borders washington and oregon? what is name of the north american river that forms the border between the states of oregon and washington? what is the river between washington and oregon? what is the river that separates the states of washington and oregon? what is the river that forms a border between the states washignton and oregon? what is the river that forms a border between the states of washington and oregon?