Drive about seven miles up Potosi Road out of Pony, turn onto South Willow Creek Road, and you'll eventually pass a house with a No Trespassing sign nailed to a fence post. Half the hot springs guides still online tell you to ignore it, park by the main house, and knock. Do that today and you'll probably just stand on someone's porch. Potosi Hot Springs Resort changed hands in 2023, and the new owners told the Billings Gazette at the time that they planned to use the eighty-acre property as a private retreat and not run it as a business. The pools that guide writers describe knocking on a door to reach haven't been open to walk-up visitors since.
What almost none of those guides mention clearly is that a completely different hot spring sits less than a mile farther up the same drainage, on national forest land, free, and open to anyone who parks at Potosi Campground. Locals call it Upper Potosi. It's a rock-walled, gravel-bottomed soaking pool along South Willow Creek, fenced with lodgepole rails to keep cattle out, and it has never required an owner's permission to use.
Two hot springs, roughly a mile of gravel road apart, one private and one public, and the internet keeps merging them into a single confusing set of directions.
The Resort and the Campground Are Not the Same Stop
Potosi Hot Springs Resort sits closer to Pony, off South Willow Creek Road, where the main house and four rental cabins are. The resort's outdoor mineral pool runs around 93 degrees next to a wood-burning sauna, with a smaller indoor river-rock tub reached by a short uphill walk. Current listings describe it as a cabin-rental property, not a walk-in soak. If you want to use those pools, you book one of the four cabins, and the pools come with the stay. Day visitors aren't accommodated, aside from occasional public soaking days the resort announces informally during summer.
Keep driving past the resort, another mile or so up South Willow Creek Road to the Potosi Campground and Picnic Area, and a short walk from the parking area gets you to Upper Potosi. No booking, no house to knock on, no fee. Clothing is optional and dogs are welcome on leash, though they're asked to stay out of the pool itself.
The confusion isn't really anyone's fault. For years, the resort operated more like a public destination, and a lot of the hiking and hot springs content written during that era is still the first thing that comes up in a search. The rules changed in 2023. The internet hasn't fully caught up.
Quick reference if you're heading out this week:
- Potosi Hot Springs Resort — private cabin rental, pools included with a booked stay, no day-use soaking
- Upper Potosi — free, public, primitive pool at Potosi Campground, roughly a mile past the resort on South Willow Creek Road
The Deadline That Actually Matters Right Now
None of this is worth sorting out if the road is about to close for the season, and that's the part locals track more closely than which pool takes walk-ins. The window for driving into the Tobacco Roots without four-wheel drive typically holds through late September into early October, when aspen color peaks and crowds thin out, but that same stretch carries the highest weather risk of the year. Forest Service roads in this range are generally passable through the first part of October, then start closing as snow moves in. Late September, which is where the calendar sits right now, is close to the end of that window rather than the middle of it.
If you're combining a soak with a hike, the other drainage worth knowing is North Willow Creek, which leaves from a different trailhead near Pony and climbs toward Hollowtop Lake at the base of the range's highest peaks. The first mile and a half of that trail is open to ATVs and dirt bikes, a detail that surprises hikers expecting quiet alpine solitude from the first step. Past that point, it's foot and horse traffic only, and the noise drops off fast. Weekday mornings are the quiet option if the multi-use lower section isn't your idea of a good start to a hike.
South Willow Creek Road, the one that leads to both hot springs, is a separate route out of town, and it varies in quality from graded gravel to rough and unpaved toward the end. Neither road benefits from waiting. Once the first real snow hits the high country, both effectively shut down until spring.
Where the Day Ends in Pony
However the hike or the soak goes, most people passing through end up back in town before dark, and Pony doesn't offer many options for that, which is part of its appeal. The Pony Bar, on Broadway Street, is cash only and keeps an ATM inside for anyone who forgot. It hosts live music most weekends, often with Tessy-Lou or her mother, Montana Rose, and there's a hitching post out front for anyone who rode in on horseback rather than drove. Next door, the Cook Shack serves hot dogs and hamburgers Thursday through Sunday, roughly five to ten in the evening, which covers dinner for most hiking schedules without much planning required.
If you're stocking up before heading out rather than winding down after, Harrison is the stop, six miles east on Highway 283. Town Haul Diner is open weekday mornings through early afternoon and closed on weekends, so it's a better bet before a Tuesday hike than a Saturday one. Pony Express-O, a coffee hut in the same stretch of Harrison, opens around seven and closes early afternoon, serving hot and cold drinks with pastries for anyone getting an early start toward the trailhead.
None of these are seasonal pop-ups built around fall color. They're the same small handful of places that keep Pony running the rest of the year, which is why getting the hot springs question right matters more than it might seem. A short fall window, a long gravel road, and a mixed-up set of directions is a bad combination if you're trying to make the most of the days before the pass closes for winter.
The two springs sit less than a mile apart on the same road. Only one of them is still open to whoever shows up.
Pony's outdoor season runs on a short, specific calendar, and knowing which roads, trails, and hot springs are actually open this week is the kind of local detail that doesn't show up on a map. If you're thinking about property in the Tobacco Roots or anywhere else in the Madison Valley and want someone who tracks these details year-round, Dawn Myrvik can walk you through what the season actually looks like on the ground.
