The Yellowstone River is 671 miles long. It is the longest undammed river in the lower 48 states. The headwaters of the Yellowstone are outside the southeast park boundary on Younts Peak (Wyoming) and flows into Yellowstone Lake. It leaves the lake at Fishing Bridge, and continues north-northwest until it leaves the park near Gardiner, Montana. The Yellowstone River continues north and east through Montana and joins the Missouri River just across the North Dakota state line. Its watershed drains one-third of the state of Montana. It carves out the Grand Canyon of the Yellowstone in the middle of the park and runs over the Upper and Lower Falls and is home to Yellowstone cutthroat trout.
671 miles Yellowstone River is 671 miles long. 671 miles long.
671 miles Yellowstone River is 671 miles long. 671 miles long.