What a lovely hike that I highly recommend. Cottonwood Creek is one of several canyons on the western side of the Bighorns. The turnoff is just past the bridge over the reservoir on U.S. Highway 14 Alt. This is the Little Mountain Travel Management area on BLM lands. A newish looking campground, equipped with nice outhouses and even a pergola dedicated to Senator Craig Thomas (no water though) makes an overnight stay inviting so you can explore all the other back roads and canyons.
I did this as a day hike. The trail runs parallel to the creek, where of course Cottonwoods grow, as well as Willows, Serviceberries, Chokecherries, Big Sage, Mountain Maples, and a shrub I couldn’t identify.
These photos don’t do the Canyon justice. It is striking, overwhelming in its’ beauty, with massive, impressive cliffs and waterfalls surrounding your climb higher and deeper into the canyon. The trail eventually reaches the Forest Service boundary.
I am so lucky to live in such a diverse area, with the playground of the high desert of the Bighorn Basin, Yellowstone and the Absarokas to the West, the Beartooths to the North, and the lovely Bighorns and sacred Pryor Mountains to the East.