Lone Star Geyser Trail

Lone Star Geyser Trail is a 4.8-mile (7.7 km) out-and-back from Lone Star Trailhead (OK1) to the place where Lone Star Geyser comes into view, then back the same way. The mostly level route follows an old service road beside the Firehole River, with patchy pavement and dirt sections. Plan on 2 to 3 hours of walking, and add time if you want to wait for an eruption. The National Park Service describes it as wheelchair and mobility-device accessible, though the pavement is intermittent. An older trailhead listing gives 5.4 miles instead of 4.8, so treat the distance as approximate and leave a little margin.

A short early spur leads to a diversion dam on the Firehole; stay on the main route toward the geyser. Farther along, the road crosses a bridge and passes a short spur to Halfway Group at about three-quarters of a mile. At roughly 1.5 miles, Spring Creek Trail branches off; keep to the main Lone Star route. These side trails lead elsewhere, so check the junctions before turning. The forest stays close along much of the river walk, then opens around the geyser basin.

The payoff is a 12-foot cone of silica sinter in an open thermal clearing beside the river. Lone Star erupts on average about every three hours, sending water and steam roughly 45 to 50 feet high. That is an average interval, not a timetable: the cone may be quiet when you arrive, and a good eruption can mean a long wait. Its unusually steady rhythm has been observed since at least the 1880s. Silica dissolved in the hot water settles out as it reaches the surface, gradually building the cone.

The mapped trail ends at a barrier about 300 feet from the cone, where the geyser is visible. If it erupts, the clearing gives you an open view of the plume against the forest. The route continues beyond the geyser toward Howard Eaton, Shoshone Lake and Continental Divide Trail connections; that adds a longer backcountry walk, not part of this standard outing. Cyclists share the road to the barrier and must dismount before the geyser.

Stay on established paths around the basin. The crust can be thin above scalding water, and stepping onto unmarked ground can be fatal. Pets are not allowed on the trail. Bears and bison use this area: keep at least 100 yards from bears and wolves and 25 yards from bison and other wildlife.

Lone Star Trailhead is just beyond the Kepler Cascades pullout, southeast of Old Faithful. The small lot can fill; Kepler Cascades parking is the nearby overflow option. The trailhead has an information kiosk and vault or composting toilet. No food or potable water service was confirmed at the access, so do not count on finding either along the walk. There is no separate activity fee or reservation, though Yellowstone entrance fees may apply.