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⏵ Course guide · Montana ultra

Bob Marshall Trail 50K Course Guide

The Bob Marshall Trail 50K is a two-lap mountain 50K out of the Seeley Creek Ski Trails near Seeley Lake, right on the edge of the Bob Marshall Wilderness. The climbing is moderate, but you run the same loop twice, so the rugged wilderness singletrack and the open road both come back around on tired legs. I will walk you through one lap of the course first, then give you a pacing and fueling plan built for doing it twice. There are free calculators along the way to dial in your own numbers.

⏵ At a glance

Bob Marshall Trail 50K quick facts

Date
Saturday, July 18, 2026
Location
Seeley Creek Ski Trails, Seeley Lake, MT, on the edge of the Bob Marshall Wilderness
Distances
50K, Marathon, 25K, Half Marathon, 10K, 5K (the 50K is two laps of the 25K loop)
Elevation gain
50K: about 2,600 ft total over the two laps (no big single climb, lots of rolling trail)
Start
9:00 AM (all distances start together)
Cutoff
First loop by 1:30 PM (4.5 hr); finish within the posted overall limit
Surface
Groomed Nordic ski trails, a Forest Service road, and rugged wilderness singletrack (no pavement)
Qualifier
No Western States, Hardrock, or UTMB qualifier status listed by the race

These facts come from the official race page and the UltraRunning listing. Check the current date, the overall cutoff, and the aid stations in the race-day details before you commit. Race logistics change year to year.

The course: one loop, run twice

The 50K is two laps of the same 25K loop, about 2,600 feet of climbing across the day with no single big pass. Each loop has three distinct sections: the groomed Seeley Creek ski trails, an open Forest Service road, and a chunk of rugged singletrack along the Bob Marshall Wilderness boundary. Knowing the loop cold the first time through is half the battle, because you get to run the whole thing again on heavier legs.

The ski trails: smooth, fast, and a trap if you let it be

The first 10K of each loop runs on the Seeley Creek Nordic ski-trail system, with only about 475 feet of gain and loss. This is the smoothest, most runnable footing of the whole day, and that is exactly why it can wreck you. It feels easy, so it is tempting to bank time here, especially on lap one with fresh legs and the cutoff in the back of your mind. Hold yourself back. The smart move is to roll through this section relaxed and let it be the part that feels good on lap two, not the part you paid for.

The Forest Service road: the open climb and the aid station

After the ski trails the course climbs onto an open Forest Service road for about 4.5 miles, gaining around 450 feet. It is not steep, but it is exposed, and in mid-July the Montana sun on an open road is the real heat of the day. The one fully staffed aid station sits out here around mile 6.5 to 7 of the loop, and as a 50K runner your drop bag gets delivered there, so this is where you refill and restock both times around. Treat the road as the spot to drink, eat, and manage your temperature, not the spot to surge.

The wilderness singletrack: where the loop gets rugged

The last stretch of each loop is a few miles of lightly maintained singletrack that parallels the actual Bob Marshall Wilderness boundary, and it drops a few hundred feet on the way back toward the start. This is the rugged, technical part: narrow, rooty, rocky in places, the kind of trail that asks for quick feet and attention. Fresh, it is a fun piece of trail. On lap two, with tired legs and the day getting long, this is where sloppy footwork turns into stubbed toes and slow miles. Practice running technical singletrack tired so this section does not fall apart on you the second time through.

Pacing strategy for a two-lap 50K with a hard first cutoff

With moderate climbing split across two identical laps, this race is won by even pacing and a clean first loop, not by hammering. The 1:30 PM first-loop cutoff means you do have to keep lap one moving, but the bigger mistake is going out so hard that lap two becomes a death march. Run the first loop with a little in reserve.

Pace by effort, not by your flat-ground splits

The ski trails will tempt you into road pace and the open road climb will quietly cost you more than it feels like, so run the whole loop by effort, not by the watch. Hold a steady, conversational output on the climbs and the rollers, and let the technical singletrack slow you down without fighting it. The classic two-lap blowup is banking a fast first loop, then watching the second one fall apart mile by mile. Use a grade-adjusted pace to turn your real fitness into honest targets for the road climb and the rolling ski trails, and you will keep lap two close to lap one.

Build a finish prediction and back it into the cutoff

Do not guess your time off a flat road 50K. The rugged singletrack, the exposed road, and the simple fact that you run everything twice all add real time over a fast course. A vert-aware finish prediction gives you a realistic window, and from there you can back into the first-loop cutoff and know exactly what pace keeps you safely ahead of 1:30 PM without burning matches. Plan to come through the first loop with a comfortable buffer, not right on the line.

⏵ Free tools to pace this course

Fueling strategy for the heat and the sparse aid

Most runners are out on this 50K for somewhere around 5 to 8 hours, with only one staffed aid station per loop and a hot, open road section in the middle. That makes carrying your own carbohydrate, sodium, and fluid as important as your fitness. Your drop bag at the road aid station is where you reload both laps.

Carbs: steady, trained, and in your pack

For a 5 to 8 hour effort, aim for around 60 to 90 grams of carbohydrate per hour, and only push the higher end if your gut is trained for it. Because there is just one staffed aid per loop, you cannot count on grabbing calories every few miles, so carry gels or chews and keep eating on a clock instead of waiting for the next table. Stage your favorites in the drop bag at the road aid station so you restock the same way on both laps. Practice your exact race-day carb rate on hot long runs so it feels routine, not like an experiment.

Sodium and fluid: plan for the open road in July

The exposed Forest Service road in the midday Montana sun is where you lose the most fluid and salt, so plan for the heat even though the elevation gain is modest. Lean toward the higher end on sodium, often around 500 to 700 milligrams per liter of fluid, and more if you are a heavy or salty sweater. Carry enough water to cover the gap from the start through the road aid and back, twice, rather than rationing to the next stop and arriving empty. Weigh yourself before and after a hot long run to find your real sweat rate, then build the plan around your own number.

⏵ Build your fueling plan

Get a carb, sodium, fluid, and caffeine plan per hour built for your weight, your goal time, and the Bob Marshall heat with the free ultra fueling calculator. Browse the rest of the free running tools at the tools hub.

⏵ Train for it with Summit Line

Get a race-day plan built around YOUR fitness, this exact Bob Marshall two-lap course, and your projected splits. Summit Line reads your real training, builds a plan for the repeat loop, and rehearses your fueling so race day is something you execute, not guess at.

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Bob Marshall Trail 50K FAQ

How hard is the Bob Marshall Trail 50K?

It is a real mountain 50K but the climbing is moderate by ultra standards, somewhere around 2,600 feet over the full distance, spread across rolling trail rather than one brutal pass. The harder part is the format and the footing: the 50K is two laps of the same loop, so you hit the rugged wilderness singletrack and the ski-trail rollers twice, and you face them the second time on tired legs. July in Montana can also throw real heat at you up on the open Forest Service road. If you respect the first-loop cutoff of 1:30 PM and pace the first lap honestly, most prepared runners can get a strong second lap out of it.

How much climbing is in the Bob Marshall Trail 50K?

Roughly 2,600 feet of total gain across the two laps, so call it about 1,300 feet per loop. There is no single signature climb here. Each loop rolls through the Seeley Creek ski-trail system (about 475 feet of gain and loss in the first 10K), climbs gently along a Forest Service road (around 450 feet over about 4.5 miles), and then drops into a stretch of wilderness-boundary singletrack. It adds up through repetition more than through any one wall, so the climbing is steady and runnable rather than a leg-breaker.

What are the cutoff times for the Bob Marshall Trail 50K?

The one you have to plan around is the first-loop cutoff: you need to finish your first 25K loop by 1:30 PM, which is 4.5 hours after the 9:00 AM start, or you are pulled from the race. After that you continue onto the second loop and need to come in under the posted overall finish limit for the day. The exact overall cutoff has been listed differently year to year, so check the current race-day details and confirm the finish deadline before you start.

What is the course like at the Bob Marshall Trail 50K?

Each lap has three distinct sections. You start on the groomed Seeley Creek Nordic ski trails for the first 10K, which is the smoothest, most runnable footing of the day. Then you climb onto an open Forest Service road for about 4.5 miles, which is where the full aid station sits around mile 6.5 to 7. The last piece is a few miles of lightly maintained singletrack that parallels the actual Bob Marshall Wilderness boundary, and that is the rugged, technical part. The 50K runs that whole loop twice. There is no pavement anywhere on the course.

How many aid stations does the Bob Marshall Trail 50K have?

It is a low-support, backcountry-style race, so do not expect aid every few miles. There is one fully staffed aid station out on the Forest Service road around mile 6.5 to 7 of each loop, plus the start and finish area you pass through between laps. 50K runners get a drop bag that is delivered to the primary aid station, so you can stage your own nutrition there. Because the aid is sparse, carry enough fluid and calories to cover the long gaps, especially across the exposed road section in the July sun.

Is the Bob Marshall Trail 50K a good first 50K?

It is a reasonable choice for a prepared first-timer. The climbing is moderate, the ski-trail sections are forgiving, and a two-lap course means you see the whole route once before you have to do it on tired legs, which is mentally easier than a strange point-to-point. The honest cautions are the rugged wilderness singletrack, the sparse aid, and that 1:30 PM first-loop cutoff, so you cannot dawdle on lap one. Train some time on technical trail, rehearse carrying your own fuel and water, and pace the first loop with the cutoff in mind, and it is a friendly place to go long for the first time.

This guide is independent and for planning only. The course details, dates, cutoffs, and aid stations come from public sources and can change year to year, so confirm the current specifics with the official race before you register or run. The fueling and pacing advice is general and not medical advice.