Summit Line

⏵ Course guide · Colorado ultra

High Lonesome 100 Course Guide

The High Lonesome 100 is one of the best modern mountain 100s in the country, a single loop through the Sawatch Range on the Continental Divide and Colorado Trails, past old ghost towns and over five alpine passes. It is high, it is exposed, and it asks you to climb and descend all day and night in thin air. I will walk you through the course first, then give you pacing and fueling strategy built for the altitude and the night, plus the crew and pacer logistics and free tools to dial in your own numbers.

⏵ Quick facts

High Lonesome 100 at a glance

Date
Fri, July 17, 2026 (into Sat, July 18)
Location
Sawatch Range / Continental Divide, base of Mount Princeton near Nathrop, Chaffee County, CO
Distance
About 100 miles, a single loop
Elevation gain
Roughly 23,500 ft of climbing
High point
About 13,100 ft, with five alpine passes
Start
6:00 AM MDT
Cutoff
37 hours overall, plus intermittent aid-station cutoffs
Entry / qualifier
Lottery entry · Hardrock 100 and Western States qualifier

Note: exact mileage, vert, aid stations, and the route get tweaked year to year, and entry is a low-odds lottery. So before you plan your race, confirm the date, course, cutoffs, and entry rules on the official High Lonesome 100 site.

The course

High Lonesome is a single big loop starting and finishing in an open meadow at the base of Mount Princeton near Nathrop, in the Sawatch Range of central Colorado. It is mostly singletrack, with chunks on old mining roads, and it strings together long stretches of the Continental Divide Trail and the Colorado Trail through high basins, over ridgelines, and past the ghost towns of St. Elmo and Hancock. About 100 miles, roughly 23,500 feet of climbing, five alpine passes, and an average elevation north of 10,000 feet. The high point sits around 13,100 feet.

It is all high: the altitude is the real course

The defining feature of this race is not one famous climb, it is that the whole thing lives up high. You average over 10,000 feet for the entire loop, you spend about 15 percent of it above tree line, and you top out near 13,100 feet on the passes. That changes everything. Climbs that would be routine at home feel like a different sport in air this thin, and your pace, your breathing, and your stomach all pay the altitude tax from the first mile.

If you live at sea level, this is the part to respect most. Come in with whatever altitude prep you can manage, pace the early climbs by breathing and effort instead of by your flatland numbers, and accept that you are going to move slower up high than your fitness says you should. The mountains do not care how fast you are on a treadmill.

Five passes, two ghost towns, and the big basins

The loop climbs over five alpine passes and rolls through remote high basins and along soaring ridgelines, with the historic ghost towns of St. Elmo and Hancock tucked into the route. The footing mixes smooth Colorado Trail singletrack with rockier high country and old mining-road grades. It is gorgeous, genuinely some of the best trail in the state, but big views and above-tree-line ridgelines also mean real exposure when the weather turns.

The Hancock aid station, up high near the old townsite, has become a bit of a legend in its own right and lands around the halfway point of the loop. Mentally, breaking the race into the passes helps: get over each one steady and intact rather than chasing a split, because the climb after this one is always coming.

Afternoon storms and the long night

July in the Colorado high country means afternoon thunderstorms, and when you are above tree line that is not a minor thing, it is a safety issue. Lightning, sudden cold, hail, and wind can all show up fast. Try to time the highest, most exposed sections for earlier in the day when you can, watch the sky, and know the race may hold or reroute you if the weather gets dangerous up top.

Then there is the night. You will be out for at least one full night, much of it high and cold, and the back half of a mountain 100 in the dark at 11,000-plus feet is where the lonely in High Lonesome earns its name. Warm layers, a reliable headlamp with a backup, and a plan to keep eating in the dark are not optional. This is where pacers and a good warm drop bag matter most.

Aid, crew, pacers, and drop bags

The course is supported by aid stations along the loop, with drop bags at the designated ones. Crew can meet you at a set of access points, and a couple of spots need a shuttle, so your crew should study the crew manual and pad their timing for mountain driving. Pull the current aid-station chart so you know the mileage and the gaps, because some high stretches between stations are long and exposed and you have to carry enough to cover them.

Pacers are allowed from the Hancock aid station to the finish, roughly the second half, and runners over 65 may take a pacer from the start. A pacer through the night, when you are cold and low and the trail is empty, is worth a lot here. The intermittent cutoffs at aid stations are enforced, so check them against your plan and keep margin, especially early, because the altitude makes the front half slower than you expect.

Pacing strategy for a high-altitude 100

A loop this high rewards patience and altitude discipline over raw speed. Pace it by effort and by grade, treat the air as a tax you cannot dodge, and protect yourself for the night.

Pace the climbs by effort, not by your flatland watch

Your sea-level pace means nothing up here, and trying to hold it is how you blow up before the night even starts. What matters is grade-adjusted effort at altitude, so settle into an output you can actually sustain up the passes and hike the steep pitches early without guilt. The classic High Lonesome mistake is feeling fresh on the first climb or two and pushing, then getting hollowed out by the thin air in the second half. Use a grade-adjusted pace to turn your real fitness into honest climbing and descending targets, then run a notch easier than that up high.

Build a vert-aware, altitude-honest finish prediction

Do not guess your High Lonesome finish off a road or even a lower-elevation trail 100. The 23,500 feet of climbing, the technical high country, and especially the altitude all add real time. A vert-aware finish prediction that accounts for this much climbing gives you a realistic window, and then you can work it back into the 37 hour clock and the intermittent cutoffs so you know how much buffer you actually have at each pass instead of hoping.

Save your legs and your head for the second night-half

The smart way to run this is to get through the first half intact, legs and stomach and head all still working, then grind out the high, dark second half. Banking time early at altitude almost never works, because anything you push for up high you pay back double when the air and the cold and the dark gang up on you. If you want to reality-check your goal against a real 100 mile mountain effort, run a recent race through the race-equivalent calculator before you commit to a number.

⏵ Free tools to pace this course

Fueling strategy for altitude and the night

High Lonesome is a long day and night in thin air, and altitude is rough on the gut. That makes steady, trained fueling and smart hydration matter as much as your climbing legs.

Carbs: eat early, keep it steady, train the gut

For an effort this long, aim for around 60 to 90 grams of carbohydrate per hour, and only push the high end if your gut is trained for it. The catch up here is altitude, which kills appetite and slows digestion, so getting calories down above tree line is genuinely harder than it is at home. Front-load a little: eat well early and through the lower stretches so you are not trying to force food when you are high, gasping, and queasy. Practice your exact hourly carb number on long runs so 70 to 90 grams an hour feels normal, not like a science experiment at mile 70.

Sodium and fluid: do not let the dry air fool you

Keep sodium in the 500 to 700 mg per liter of fluid range, more if you are a heavy or salty sweater. The tricky part at altitude is that the air is dry and cool, your sweat evaporates fast, and you can get behind on fluid without feeling thirsty, then cramp or fade. Drink to a plan, not just to thirst, and carry enough to cover the long, exposed gaps between high aid stations instead of rationing to the next one. Weigh yourself before and after a long mountain 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 a high-altitude 100 with the free ultra fueling calculator. Browse the rest of the free running tools at the tools hub.

Train for the conditions

High Lonesome asks for a lot at once: altitude, big climbing and descending, a full night, and 100 mile endurance. These guides go deep on the parts that decide your day.

⏵ Free calculators for this race

Run your High Lonesome numbers with our free, no-signup tools, then let Summit Line tie them all together with your real fitness and this exact course.

See all free running tools →

⏵ Train for High Lonesome

Get a race-day plan built around YOUR fitness, this exact course profile, and your projected splits. Summit Line reads your actual training, builds a fueling and pacing plan around the High Lonesome altitude and climbing, and tracks how your gut and legs handle the load, so race day is rehearsed instead of guessed.

Get started free →See it on a real 100 miler

High Lonesome 100 FAQ

How hard is the High Lonesome 100?

It is a hard one, and most of the difficulty is the altitude. You cover about 100 miles with roughly 23,500 feet of climbing, but the number that really matters is that the course averages over 10,000 feet and tops out near 13,100 feet over five alpine passes. You are climbing and descending all day with thin air the whole time, big stretches above tree line where there is nowhere to hide from sun or storms, and then a full night out in the high country where it gets cold fast. The 37 hour cutoff sounds generous, but the altitude and the climbing eat into it. If you do not live high or train high, the air alone can take your day apart before the climbing does.

How much climbing is in the High Lonesome 100, and how high does it get?

The loop climbs somewhere around 23,500 feet across roughly 100 miles, and it crosses five alpine passes including spots like Tin Cup, Chalk Creek, and the high country near Monarch. The high point sits around 13,100 feet and the average elevation is over 10,000 feet, so you basically never come down to thick air. About 15 percent of the course runs above tree line. The climbing itself is steady mountain climbing rather than a couple of monster walls, but doing all of it at altitude is what makes it bite. Exact figures shift a little year to year with reroutes, so confirm the current numbers with the race.

How should I fuel for the High Lonesome 100?

Plan for a long day and night at altitude, which is its own fueling problem. Most runners target 60 to 90 grams of carbohydrate per hour, leaning to the high end if the gut is trained, but altitude blunts your appetite and slows your stomach, so getting calories in up high is harder than it is down low. Keep your sodium in the 500 to 700 mg per liter of fluid range and adjust for how much you sweat, and do not let the dry, cool mountain air fool you into under-drinking. The smart move is to eat early and often before you climb above tree line, because once you are up there in the wind and the thin air, your stomach gets fussy. Run your own numbers with the free ultra fueling calculator.

What are the cutoff times for the High Lonesome 100?

The overall limit is 37 hours from the 6:00 AM start. There are also intermittent cutoffs at aid stations along the course, and they are enforced, so you cannot bank all your buffer for the end. Because so much of the race is high and slow, the early and middle cutoffs can sneak up on people who started too conservatively or who got wrecked by the altitude. Pull the current cutoff chart from the race and build your plan backward from those times with real margin, especially through the highest passes.

Do you need to qualify, and how do you get into the High Lonesome 100?

Entry is by lottery. The application window runs in late December into early January, the field caps at roughly 250 runners, and there are the usual extra paths for volunteers, legacy runners, and a handful of others. The race has earned a strong reputation fast, so it draws a deep field and getting a number is competitive. It is also a qualifying race for the Hardrock 100 and for Western States, which is a big part of why people target it. Lottery rules and qualifier status get updated every year, so always confirm the current process on the official site before you plan around it.

What about crew, pacers, drop bags, and the night?

You get a pacer from the Hancock aid station to the finish, which is around the halfway mark, and runners over 65 can take a pacer from the start. Crew can reach you at a set of access points like Hancock and Blanks, with drop bags at the designated aid stations, and a couple of spots take a shuttle to reach, so your crew needs a plan and patience. You will be out for at least one full night, much of it high and exposed, so pack real warm layers, a headlamp with backup, and the required gear. Nights at 11,000-plus feet get cold and lonely, and that is where a good pacer and a warm drop bag earn their keep.

This guide is for planning and training, and it reflects publicly available information about the High Lonesome 100. Race details, including the date, course, aid stations, cutoffs, weather, and entry and lottery rules, can change year to year. So always confirm the current specifics on the official High Lonesome 100 race website before you train or travel. The fueling and pacing advice is general and not medical advice.