Cross the Wind River Range over Togwotee Pass and drive on to Jackson Hole. Magnificent in every season, Grand Teton National Park is especially lovely in the fall. Enjoy a hike in the park, then head south toward Jackson on the Moose-Wilson Road, where wildlife ambles amid the glorious aspen stands. For a naturalist-led trek featuring a chance to see and hear rutting bull elk, contact the Hole Hiking Experience, which has been guiding area visitors since 1989.
From Jackson, continue south on U.S. Highway 89 through the Star Valley. See the arch made from 3,011 elk antlers on Afton's Main Street, then head 5 miles east out of town via Second Avenue into Swift Creek Canyon. Hike the easy 3/4-mile trail to view Periodic Spring, the only natural phenomenon of its kind in North America and one of only three in the world. The cliff-side spring naturally cycles off and on every 12 to 18 minutes – a phenomenon that led Shoshone Indians to call it "the spring that breathes." You'll enjoy catching your breath this fall in Wyoming, too.