Top Trails: Yellowstone and Grand Teton National Parks. Andrew Dean Nystrom

      Washburn Hot Springs, an optional destination for the Mount Washburn hike (Trail 18)

TRAIL 3 NORTHWEST YELLOWSTONE

       Bunsen Peak

       TRAIL USE

      Hike

       LENGTH

      4.2 miles, 3 hours, or

      7.0 miles, 5.5 hours

       VERTICAL FEET

      ±1300

       DIFFICULTY

      – 1 2 3 4 5 +

       TRAIL TYPE

      Out-and-back or Loop

       SURFACE TYPE

      Dirt

       FEATURES

      Mountain

      Summit

      Wildflowers

      Wildlife

      Great Views

      Photo Opportunity

      Geologic Interest

      Steep

       FACILITIES

      None

      This scenic, heart-pumping ascent is a popular early-season altitude acclimatization route. Many folks hike in jeans and tennis shoes, but boots and trekking poles come in handy for the scree slopes, especially if you opt for the full loop or the steep side trip to Osprey Falls.

       Best Time

      The trail is hikable May–October: snow lingers on the trail near the summit as late as June, but the south-facing slope is free of heavy snow earlier than most peaks in the park. Other than snowmelt, there is no water along the entire route. There is precious little shade along the way, so it is best to hike early in the morning or late in the afternoon. Early afternoon thundershowers (locally known as rollers)—and lightning—are common. No matter what the weather is like at the trailhead, pack a jacket for the typically brisk weather up top.

       Finding the Trail

      From Mammoth, go 4.5 miles south on Grand Loop Road (US 89) and turn left into the gravel Bunsen Peak trailhead (1K4) parking area on the east side of the road (just past the Golden Gate). From Norris Canyon Road, go 16.5 miles north on Grand Loop Road and turn right into the parking area. Get here early to secure a space in this small and popular lot. If the parking area is full, try the smaller pullouts farther along the main road.

       Trail Description

      From beyond the service road barrier at the Bunsen Peak trailhead ▸1 parking area, the singletrack earthen trail splits off from Old Bunsen Peak Road at a signed junction ▸2 opposite a few waterfowl-rich ponds. Just up the hill through some sagebrush, a notice board ▸3 has a map of trails in the Mammoth region.

       The patchwork “burn mosaic” pattern left by the 1988 fires, most evident from Grand Loop Road, demonstrates how supposedly catastrophic fires can actually open up new ecological niches.

      The doubletrack gravel trail winds gently up through lodgepole pines in a regenerating burn mosaic created by the 1988 North Fork Fire. Thanks to the burn, in spring and summer this section is often festooned with wildflowers. The trail climbs scenically above Rustic Falls and the Golden Gate, with the Howard Eaton Trail sometimes visible off to the left above the rocky white jumble known as The Hoodoos.

      Viewpoint

      From here, you can also spot your destination atop Bunsen Peak, just to the right of the telecommunications equipment. Behind you are expansive views back over Gardner’s Hole, Swan Lake Flat, and beyond to the Gallatin Range. The trail flattens out through an area dotted with snags as it swings away from Grand Loop Road and heads for the summit.

      Wildlife

      Viewpoint

      As you climb through remnants of a mature spruce–fir forest on the southwest-facing slope, heading toward the first switchbacks, watch for the stoic bighorn sheep (some with radio collars) that inhabit the scree slopes below the summit. In the fall, you can sometimes even hear rutting elk bugling as far away as Mammoth. A little bit more than halfway up, after a couple of gentle switch-backs, there is a good overlook of the Mammoth Hot Springs area; this is near the Cathedral Rock ▸4 outcropping after 1.2 miles.

       OPTIONS

       Osprey Falls and Loop Trails

      To make this trail into a loop, drop down the east side of Bunsen Peak after summiting, and return to the parking area via the Old Bunsen Peak Road, a wide, relatively flat, paved service road that is now unused. This abandoned road is also a popular cross-country ski route; the northern end is an alternative trailhead that is used by park employees but is largely inaccessible to park visitors. Plan on about five hours for the full loop, plus 2.8 miles and an extra couple of hours if you opt to take the steep detour down to Osprey Falls.

      Steep