The ride begins in a tunnel long enough to change your idea of a casual bike outing. The St. Paul Pass, also called the Taft Tunnel, runs roughly a mile and a half at the Idaho-Montana border, and entering it means leaving daylight behind for a cold, damp stretch of former railroad route.
A dependable bike light or headlamp turns the darkness into a moving little pool of visibility: gravel ahead, wet walls alongside, the occasional glint of moisture. It is a memorable opening, especially for children old enough to handle their bikes comfortably and adults who still appreciate a bit of harmless theatricality on an afternoon ride.
Then the tunnel releases riders onto a broad gravel trail that follows an abandoned railroad grade through mountain country. The downhill direction is gentle rather than steep, with easy curves and long stretches where the pedals can take a break.
A Railroad Grade Built for Coasting
This is mountain biking in the broadest, friendliest sense of the phrase. The surface is smooth gravel, the grade is shallow, and the route was built for trains before it was ever used by bicycles. That old engineering makes a practical difference: a family group can spend more time looking around and less time wrestling with difficult terrain.
The one-way route is generally about 14.5 to 16 miles, depending on the arrangement and route description. Riders who want the full workout can make it a nearly 30-mile round trip by pedaling back uphill, but many choose the downhill ride and a return shuttle for themselves and their bikes.
Basic bicycle control still matters. The trail passes through dark tunnels, crosses elevated trestles, and includes canyon-side terrain, so it is better suited to riders who can steer, brake, and stay composed on a bike than to someone taking a first-ever ride. For a multigenerational outing, that is an important distinction.
Standard bikes are one option, but the rental mix has also included e-bikes, beach cruisers, and trikes. A trike can be a welcome alternative for someone who does not feel steady on a conventional bicycle, and seating can be adjusted or changed when comfort becomes more important than style somewhere around mile eight.
The Long, Wet Opening Tunnel
The Taft Tunnel is not a quick underpass. It is a substantial piece of railroad engineering that took years to construct, and riding through it gives the day an immediate sense of scale. The temperature drops, the air turns wet, and the route ahead disappears beyond the reach of ordinary daylight.
Layers are useful here, even on a warm mountain afternoon. The tunnel can be cold and muddy, and a light waterproof layer or poncho is sensible for the dampness. Clothing that can handle a little grime is also a good choice.
A thin stripe of mud on the back of a rider's pants is a fairly ordinary souvenir, particularly when tires move quickly over wet ground. It is not a glamorous detail, but it is one of the practical facts of the route—and a small reminder that this is an old rail corridor through actual mountain weather, not an indoor attraction.
Bike lights illuminate the tunnel, but bringing a bright personal light is still worthwhile. It helps riders see their own path clearly and can be especially useful if the shuttle routing has them ride through the long tunnel again on the way back to the vehicle area.
Seven Trestles Above the Trees
After the close, enclosed feeling of the tunnels, the trestles open the day back up. The route includes seven high railroad trestles, and some rise above the tops of nearby trees. One minute riders are rolling through forest; the next they are suspended over a broad sweep of slope, canyon, and distant ridgeline.
The bridges create natural stopping points, both for photographs and for simply looking over the railings for a minute. The mountain scenery shifts as the route drops: forested hillsides, open overlooks, water below in places, and the long geometry of the old railroad line stretching ahead.
These crossings also keep the ride from becoming a single long gravel glide. A tunnel changes the air and light. A trestle changes the height and view. Then the trail settles back into the trees until the next surprise arrives.
Children need close attention on the elevated sections, and adults will want to keep the group moving in an orderly way rather than spreading across the trail. The setting is exciting precisely because it is high and exposed in places.
A Route With Its History Still Attached
The railroad is not merely background decoration here. It explains the unusual character of the ride—the gentle grade, the enormous tunnel, the repeating trestles, and the way the route threads terrain that would be much more demanding on an ordinary mountain trail.
Historical markers help fill in the story of the line and its construction. Guide commentary can add another layer, especially for riders taking the shuttle back, with local history and nature information delivered alongside a little humor.
That combination makes the outing work well for groups with mixed interests. One person may come for the bike ride, another for the railroad history, and someone else for the views. Nobody has to be an advanced cyclist to have a full afternoon.
Wildlife and the Long View Downhill
The pace leaves room to notice the landscape. Because much of the route is downhill and easy to pedal, riders can coast for extended stretches, pause at overlooks, and take their time on the bridges instead of treating the day as a race.
Wildlife sometimes appears near the water or along the forested sections. Moose have been spotted on the route, though no one should count on a particular animal encounter. The more dependable companion is the scenery: timbered slopes, mountain air, and the curious pleasure of traveling through country once crossed by trains.
There are frequent reasons to stop with a camera or phone. The tunnel entrance has its own drama, the trestles supply the big panoramic moments, and the former rail line itself makes a strong leading line through the landscape.
Shuttles, Snacks, and a Manageable Day Out
At the lower end, riders can load bicycles onto a return shuttle or decide to make the uphill ride back under their own power. The shuttle changes the character of the outing: instead of saving energy for the return climb, a family can put it toward tunnel stops, bridge views, and a more relaxed pace on the descent.
Maps and route descriptions are useful because the sequence of trail riding, shuttle transport, and possible return passage through the first long tunnel can vary with the arrangement. The total outing commonly takes much of an afternoon once photo stops, food, and transportation are included.
Food is available near the lower end of the trail, though bringing a snack is still a comfortable way to avoid depending on a single stop. Cell service may disappear along portions of the route, another good reason for everyone in a group to understand the basic plan before rolling out.
Advance online reservations are commonly used for rentals and tickets. Equipment choices and shuttle arrangements can vary, and e-bike transport may carry an additional charge.
A Different Ride After Dark
Moonlight rides offer a nighttime version of the route, giving the tunnels and trestles a different mood. In the dark, personal lighting becomes even more central, and the familiar railroad corridor turns into a string of lit gravel, shadowy trees, and open mountain silhouettes.
For daytime riders, the trail already provides plenty of adventure without technical mountain-bike demands: a long cold tunnel, high bridges, a mostly downhill grade, and a shuttle waiting at the far end for those who would rather save the climb for another day.