▸9 5.25 Start of Old Gardiner Road
▸10 5.5 Return to trailhead parking areas
TRAIL 2 NORTHWEST YELLOWSTONE
Boiling River
TRAIL USE
Hike
LENGTH
1.0 mile, 1–2 hours, including soaking
VERTICAL FEET
Negligible (±300)
DIFFICULTY
– 1 2 3 4 5 +
TRAIL TYPE
Out-and-back
SURFACE TYPE
Dirt
FEATURES
Child Friendly
Handicap Access
Stream
Swimming
Geothermal
FACILITIES
Restrooms
Picnic Tables
Yellowstone’s premier frontcountry soak is a dynamic series of five-star hot pots formed by the confluence of an icy river and an impressive thermal stream. It’s fun for the entire family and, as one of few remaining places to legally soak in the US national parks, it’s definitely not to be missed.
Best Time
Soaking in the mix of cool and near-boiling water is most enjoyable in early morning or late afternoon and best avoided in the midday summer sun. Visiting in the winter is a special treat. The area is normally open for soaking July–April, but access is restricted by the National Park Service (NPS) during periods of high spring runoff.
Finding the Trail
The springs do not appear on official NPS park maps and are not named on most other maps, but they are still easy to find. The unsigned turnoff for the parking areas is off the North Entrance Road, almost exactly halfway between the North Entrance gate and the Mammoth Hot Springs Junction, 2.3 miles from either point. Officially, these are the parking areas for the Lava Creek Trail, which leads to the bathing area. The only signs near the parking areas—the main one on the east side of the road and an overflow lot with shady picnic tables on the west side—announce the Wyoming–Montana state line (if headed south from Gardiner) and 45TH PAR ALLEL OF LATITUDE: HALFWAY BETW EEN EQUATOR AND NORTH POLE (if headed north from Mammoth). The signed Lava Creek trailhead (1N3) is on the northeast side of the road, behind the restrooms on the far east side of the gravel parking lot.
The 45th parallel also passes through Minneapolis–Saint Paul, Nova Scotia, Bordeaux, the Black Sea, the Caspian Sea, Mongolia, and the northern tip of the Japanese islands.
Logistics
The Boiling River is generally open for soaking sunrise–sunset, or as late as 5 a.m.–9 p.m. in the high season. Check with the visitor center in Mammoth for the current status. Even though there are few signs, the area is one of the park’s worst-kept secrets and receives up to 200 visitors per day.
Bring drinking water, hiking sandals (flip-flops will fall off in the river), and a towel, plus a flashlight if visiting around sunset. The only changing area is inside the restroom at the trailhead.
Trail Description
Stream
From the far east side of the main parking area ▸1 on the east side of the North Entrance Road, a wide, flat gravel path heads upstream alongside the Gardner River (yes, the river and the town of Gardiner are spelled differently, for no good reason except that Montana is quirky) for about half a mile.
Mammoth Campground Trail
If you are staying at Mammoth Campground, it’s worth knowing that an alternative path, which is roughly as long as the trail from the parking lot but much steeper, descends 250 feet in elevation from the far northeastern corner of the camping area. The unsigned trailhead is across the North Entrance Road, to the left of the prominent Dude Hill, but there’s no parking here. It’s not uncommon to confuse this route with the signed Lava Creek Trail that starts at a turnout parking area just to the south. The campground office can point you in the right direction.
The steep, unnamed path from the Mammoth Campground ▸2 joins the Lava Creek Trail (also called the Boiling River Trail) just before the main trail winds around the thermal source that emanates from an off-limits cave, thought to be resurfacing runoff from distant Mammoth Hot Springs. The official Boiling River soaking area, ▸3 indicated by split-rail log fencing, is at the far end of the trail, 0.5 mile from the trailhead.
To keep the Boiling River family friendly, a couple of rules are strictly enforced: bathing suits are required, and alcohol is prohibited.
Geothermal
Signs warn of the possible presence of the pathogenic bacteria Naegleria fowleri, but no cases of the rare meningitis caused by the microscopic amoeba have ever been reported here. Just to be safe, do not submerge your head or nose below the water—the amoeba enters the brain via the nasal passages. Symptoms include a runny nose, a sore throat, a severe headache, and in the worst cases, possible death within a few days.
Swimming
Bathing in the near-scalding main thermal channel would be fatal and is prohibited. (See “Bathers Beware”). The actual composition of the dynamic bathing area changes daily and with the seasons. Seek out spots where other soakers are congregating, and beware of direct contact with undiluted thermal water. If you have trouble finding a calm spot where the current does not wash you downstream, try placing a big river stone in your lap.
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