ORIGINATING HIGH IN THE INTERIOR OF YELLOWSTONE NATIONAL PARK AT THE YELLOWSTONE LAKE IN WYOMING, THE YELLOWSTONE RIVER FLOWS 676 MILES TO ITS CONFLUENCE WITH THE MISSOURI RIVER - UNRESTRAINED BY A SINGLE DAM. EVENTUALLY, THE YELLOWSTONE RIVER JOINS THE MISSOURI RIVER JUST PAST THE BORDER WITH NORTH DAKOTA.
The Yellowstone River is a tributary of the Missouri River, approximately 692 miles (1,114 km) long, in the western United States. Considered the principal tributary of the upper Missouri, the river and its tributaries drain a wide area stretching from the Rocky Mountains in the vicinity of the Yellowstone National Park across the mountains and high plains of southern Montana and northern Wyoming.