Bighorn River Wind River Canyon near the town of Thermopolis. From there, the river flows through the Bighorn Basin in north central Wyoming, passing through Thermopolis and Hot Springs State Park. At the border with Montana, the river turns northeast, and flows past the north end of the Bighorn Mountains, through the Crow Indian Reservation, where the Yellowtail Dam forms the Bighorn Lake reservoir. The reservoir and the surrounding canyon are part of the Bighorn Canyon National Recreation Area. The Little Bighorn River joins the Bighorn near the town of Hardin, Montana. Approximately fifty miles farther downriver, the Bighorn River ends where
Little Bighorn River along the tributaries commonly use the shortened version—Little Horn—instead of the more cumbersome name, Little Bighorn. A historical variant name for the Little Bighorn is the Greasy Grass. From the 1500s to the 1800s, the indigenous Crow people knew the river as the Greasy Grass. Crow tribal historian Joe Medicine Crow explained in a 2012 YouTube interview that this name was used by the Crows for the river system because in the river bottoms in the upper reaches of the Little Bighorn and its major tributaries there was abundant grass that would gather heavy dew in the morning which, in