Bighorn River

The Bighorn River is a tributary of the Yellowstone River, approximately 461 miles (742 km) long, flowing through Wyoming and Montana. It rises in the Rocky Mountains as the Wind River, near Two Ocean Mountain, and undergoes an unusual name change at the “Wedding of the Waters” near Thermopolis, Wyoming, where it formally becomes the Bighorn River and enters the Bighorn Basin. The river's drainage covers 22,885 sq mi (59,270 km2), with an average discharge of 3,954 cu ft/s (112.0 m3/s) at Bighorn, Montana. The river flows north out of Wyoming and into Montana, where it turns northeast and passes the north end of the Bighorn Mountains. Within the Crow Indian Reservation, Yellowtail Dam impounds the river to create Bighorn Lake, with the surrounding canyon protected as Bighorn Canyon National Recreation Area. Below the dam, the Afterbay regulates downstream releases. The tailwater below Afterbay Dam is one of the most celebrated trout fisheries in the United States, supporting trophy brown and rainbow trout sustained by the cold, nutrient-rich dam releases. From the reservation the river continues northeast through the Great Plains, joining the Yellowstone River in Big Horn County, Montana, about 50 miles downstream from the confluence of the Little Bighorn.