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 led a government expedition up the Big Horn River to the mouth of Big Horn Canyon, and then southeast along the base of the Big Horn mountains. En route to the Big Horn Canyon, and about 40 miles down the Big Horn River, he camped just below the mouth of the Little Bighorn on September 6, 1859. He noted in his journal for that day that the Indian name of the Big Horn river, into which the Little Bighorn empties, is "Ets-pot-agie", or Mountain Sheep River, and this generates the name of the Little Big Horn, "Ets-pot-agie-cate", or Little Mountain