Yellowstone River

Panoramic view of Yellowstone river with reflected sky.
A view of the Yellowstone River in Hayden Valley. The Yellowstone River is the longest undammed river in the continental United States.

NPS/Neal Herbert


The Yellowstone River is the last major undammed river in the lower 48 states, flowing 671 miles (1080 km) from its source southeast of Yellowstone into the Missouri River and then, eventually, into the Atlantic Ocean. It begins in the Absaroka Mountain Range on Yount Peak. The river enters the park and meanders through the Thorofare region into Yellowstone Lake. It leaves the lake at Fishing Bridge and flows north over LeHardys Rapids and through Hayden Valley.

After this peaceful stretch, it crashes over the Upper and Lower falls of the Grand Canyon. It then flows generally northwest, meeting its largest tributary, the Lamar River, at Tower Junction. It continues through the Black Canyon and leaves the park near Gardiner, Montana. The Yellowstone River continues north and east through the state of Montana and joins the Missouri River near the eastern boundary line of the state. The Missouri River eventually joins the Mississippi River, which flows into the Atlantic Ocean at the Gulf of Mexico.

In addition to the Yellowstone River, many of the spawning streams in the Lake Village, Fishing Bridge, and Bridge Bay areas provide critical food sources for grizzly bears in the spring time. Therefore, ecologically speaking, these river and streams are a primary resource in the district. The LeHardys Rapids are a cascade on the Yellowstone River, three miles north of Fishing Bridge. Geomorphologically, it is thought that this is the actual spot where the lake ends and the river continues its northward flow. In the spring, many cutthroat trout may be seen here, resting in the shallow pools before expending bursts of energy to leap up the rapids on the their way to spawn under Fishing Bridge.

The rapids were named for Paul LeHardy, a civilian topographer with the Jones Expedition in 1873. LeHardy and his fellow survey member, Cecil Gabbett, started off on a raft with the intent of surveying the river, planning to meet the rest of their party at the Lower Falls. Upon hitting the rapids, the raft capsized, and many of the supplies were lost, including guns, bedding, and food. LeHardy and his partner saved what they could and continued their journey to the falls on foot.

Angler fishing in Yellowstone during a golden morning.
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Water flows over the Brink of Lower Falls in the Grand Canyon of the Yellwostone

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Last updated: December 7, 2022

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PO Box 168
Yellowstone National Park, WY 82190-0168



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