⏵ Course guide · Mickelson Trail rail-trail 100
The Lean Horse Ultra runs out and back on the George S. Mickelson Trail, a crushed-limestone rail-trail through South Dakota's Black Hills, just 7,162 feet of total climbing over 100 miles on gentle, forgiving grades. It is widely called one of the best first hundreds in the country. I will walk you through the rail-trail terrain first, then give you a pacing and fueling plan built for consistent running over long distance, plus free tools to dial in your own numbers.
These facts come from the official Lean Horse Ultra course information page. Aid station details and intermediate cutoffs can change year to year, so confirm the current specifics on leanhorseultra.com before you commit.
The 100 mile race starts at the Custer YMCA and runs out and back on the George S. Mickelson Trail, an old railroad grade converted to crushed limestone trail through the Black Hills. The 50 mile, 30 mile, and 20 mile races start from the Custer track and share the same out-and-back format.
A total climb of 7,162 feet, starting at 5,316 feet and topping out at 6,262 feet, is a genuinely modest profile for a 100 mile race. Combined with the crushed-limestone rail-trail surface, the course is about as runnable as a hundred miler gets: no roots, no loose rock, and grades built for the trains that once ran here rather than for maximum vert.
Removing the technical variable, difficult footing, steep unmaintained trail, lets a first-time hundred mile runner focus on the things that matter most at that distance: pacing, fueling, and mental management over a long day and night. That is exactly why Lean Horse has built a reputation as one of the best first hundreds in the country.
Even on gentle terrain, an out-and-back 100 means covering the same ground twice, and the second half runs on far more tired legs than the first. Plan your drop bags, pacer pickup points, and crew logistics around that structure, and expect your return pace to be honestly slower than your outbound pace no matter how smooth the trail is.
With just 7,162 feet of climbing and a smooth surface, the biggest pacing risk at Lean Horse is starting too fast simply because the trail lets you.
It is tempting to bank big early miles on a smooth, gently graded trail, but the fatigue of 100 miles catches up with everyone regardless of surface. A grade-adjusted pace target still matters here, even on modest grades, and holding an honest, sustainable effort from the start will beat an aggressive opening pace every time.
A vert-aware finish prediction built from your outbound pace, adjusted honestly for the fatigue you will carry into the return trip, gives you a far better read on your 32 hour cutoff margin than assuming even splits out and back. Check that projection at your turnaround point while you still have room to adjust.
⏵ Free tools to pace this course
A Friday 12:00 pm start and a Saturday 8:00 pm cutoff mean most 100 mile finishers are on trail through a warm Friday afternoon, a cool Black Hills night, and a warmer Saturday daytime stretch.
Aim for roughly 60 to 90 grams of carbohydrate per hour. Because the smooth rail-trail surface lets you maintain a more consistent effort than a technical course would, you can generally rely on a steadier per-hour fueling schedule rather than adjusting constantly for terrain changes.
Sodium in the 300 to 700 mg per liter range covers most runners, leaning toward the higher end during the warm Friday afternoon and Saturday daytime stretches. The trail's elevation above 5,300 feet means genuinely cooler overnight temperatures, so scale sodium and fluid intake down through the night before ramping back up on the second day.
⏵ Build your fueling plan
Get a carb, sodium, fluid, and caffeine plan per hour built for your weight, your goal time, and a warm-day, cool-night Black Hills rail-trail race 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 gentle rail-trail climbing profile, and your projected splits. Summit Line reads your real training, builds a plan for consistent effort over 100 miles, and rehearses your fueling so race day is something you execute, not guess at.
Yes, and it has built exactly that reputation. Lean Horse runs on the George S. Mickelson Trail, a crushed-limestone rail-trail with gentle grades and smooth, forgiving surface underfoot, a sharp contrast to the technical singletrack that dominates most western hundreds. With only 7,162 feet of total climbing over 100 miles and a full 32 hour cutoff, the course removes most of the variables, technical footing, extreme vert, that trip up first-time hundred milers elsewhere. It is widely called one of the best first 100s in the country for good reason.
The official course page lists a total climb of 7,162 feet for the 100 mile distance, starting at 5,316 feet and topping out at 6,262 feet. That is a modest elevation profile by ultra standards, and combined with the rail-trail surface, it makes Lean Horse one of the more runnable hundreds you will find, well suited to a strong, steady effort rather than technical mountain climbing skill.
The George S. Mickelson Trail is a crushed limestone rail-trail, built on an old railroad grade through the Black Hills. That means gentle, consistent grades and a smooth, predictable surface rather than roots, rocks, or loose scree. It is a genuinely different experience from most mountain hundreds, and it is a big part of why the race pulls in so many first-time hundred mile finishers.
With a Friday 12:00 pm start and a Saturday 8:00 pm cutoff, most 100 mile finishers are out for a full day, a full night, and well into a second day. Aim for roughly 60 to 90 grams of carbohydrate per hour, and sodium in the 300 to 700 mg per liter range, adjusting for South Dakota summer heat during the Friday afternoon and Saturday daytime hours. Because the smooth rail-trail surface lets you run more consistently than a technical course would, you can generally rely on a steadier per-hour fueling rhythm than you might plan for a rockier hundred. Build your numbers with the free ultra fueling calculator before race day.
The 100 mile race starts Friday at 12:00 pm and the finish line cutoff is Saturday at 8:00 pm, a 32 hour time limit. The 50 mile, 30 mile, and 20 mile events all start Saturday morning and share that same Saturday 8:00 pm finish cutoff. Given the relatively gentle terrain, a well-trained runner has real margin inside that 32 hour window compared to a technical mountain hundred with a similar cutoff.
Late July and early August in the Black Hills can run warm during the day, though the trail's elevation, starting above 5,300 feet, keeps overnight temperatures cooler than you might expect from a summer race. Plan your Friday afternoon and Saturday daytime fueling and hydration for real heat, and expect a genuine temperature drop once the sun goes down and through the overnight hours most 100 mile finishers spend on trail.
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<a href="https://runsummitline.com/guides/lean-horse-100">The Lean Horse 100 course guide</a><iframe src="https://runsummitline.com/embed/race/lean-horse-100" style="width:100%;max-width:420px;height:180px;border:0;" loading="lazy" title="Lean Horse 100 course guide by Summit Line"></iframe>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.