The land west of Mammoth [1] is some of the most rugged in Yellowstone [2], with several peaks topping 10,000 feet. Several trails cut westward across this country, one of the most interesting being the 24-mile-long Sportsman Lake Trail. The route begins at Glen Creek Trailhead five miles south of Mammoth and follows Glen Creek (a good place to see elk in autumn) for four miles before crossing into the Gardner River drainage.
Along the way, a short spur trail leads to pretty Cache Lake. Considerably more challenging is a second side trip, the climb up 10,992-foot Electric Peak, the tallest mountain in this corner of Yellowstone.
Many folks camp near Electric Peak and spend a day climbing. It’s eight miles round-trip and you gain 3,000 feet on the way up, but the trail becomes harder to follow the higher you climb.
See a park trail guidebook for details and precautions on this hike. It is possible to day hike to the top of Electric Peak from the Glen Creek Trailhead, but it’s not recommended unless you have a masochistic streak, have done a lot of hiking, and are in great shape.
Beyond the side trail to Electric Peak, Sportsman Lake Trail crosses the Gardner River twice, and there are no bridges. The water can be dangerously deep early in the summer, so this hike is generally done in August or September. After you ford the river, the trail climbs to Electric Divide (watch for bighorn sheep) and then drops steeply to Sportsman Lake and down along pretty Fan Creek to the Fawn Pass Trailhead on U.S. Highway 191.
Because this is a one-way hike you will need to set up some sort of vehicle shuttle. Another problem is bears. This country overflows with grizzly activity, and a party size of four or more is recommended for travel here. Off-trail travel is prohibited in some areas; see the Park Service for details.
Links:
[1] http://www.moon.com/destinations/yellowstone-grand-teton/yellowstone-national-park/sights/mammoth-hot-springs
[2] http://www.moon.com/destinations/yellowstone-grand-teton/yellowstone-national-park