<P> The Columbia River is the largest river in the Pacific Northwest region of North America . The river rises in the Rocky Mountains of British Columbia , Canada . It flows northwest and then south into the US state of Washington , then turns west to form most of the border between Washington and the state of Oregon before emptying into the Pacific Ocean . The river is 1,243 miles ( 2,000 km ) long , and its largest tributary is the Snake River . Its drainage basin is roughly the size of France and extends into seven US states and a Canadian province . The fourth - largest river in the United States by volume , the Columbia has the greatest flow of any North American river entering the Pacific . </P>
<P> The Columbia River is the largest river in the Pacific Northwest region of North America . The river rises in the Rocky Mountains of British Columbia , Canada . It flows northwest and then south into the US state of Washington , then turns west to form most of the border between Washington and the state of Oregon before emptying into the Pacific Ocean . The river is 1,243 miles ( 2,000 km ) long , and its largest tributary is the Snake River . Its drainage basin is roughly the size of France and extends into seven US states and a Canadian province . The fourth - largest river in the United States by volume , the Columbia has the greatest flow of any North American river entering the Pacific . </P>
what river forms part of the border between two northwestern states and flows into pacific ocean
what river forms part of the border between two northwestern states and flows into pacific ocean
Columbia River
Columbia River