Rio Grande 100 Course Guide

The altitude is the whole story

You start around 8,200 feet and basically never come back down. The average elevation is over 10,000 feet and you cross above 12,000 feet four separate times, including the climb up and over Boot Mountain. If you live at sea level, this is the thing that will decide your day. Thin air slows your climbing, blunts your appetite, wrecks your sleep, and makes every rocky descent feel harder than the grade says it should. The runners who do well here either live high or show up with a real altitude plan, and they all pace the climbs like the air is working against them, because it is.

Run the climbs by effort, hike the steep stuff early and often, and do not chase a flatland pace at 11,000 feet. The whole game is getting to the back half with your legs and your stomach still online.

Remote, minimally marked, and on you to navigate

This race is old-school on purpose. The course is marked, but the race tells you flat out that mileage is approximate and that you need to know the route ahead of time, because faint cow trails, multiple paths, and the occasional elk pulling a ribbon are all part of it. There is essentially no cell service in the La Garitas. You will cross creeks (wet feet are guaranteed), pass through cowboy gates you have to close behind you, and go long stretches seeing no one. Study the maps, run with the route in your head, and when you see markers, keep moving until the next aid shows up.

Self-reliance is not a vibe here, it is a requirement. Carry what you need to get yourself between aid stations, because help is genuinely far away.

The aid is far apart, so the gaps are the race

There are aid stations roughly every eight to thirteen miles, with names like Long Park, Pool Table, Stone Cellar, Grouse Creek, Bowers, Cow Camp, and Cathedral, and a couple of them sit hours apart by road. At ten-plus miles between aid, on slow rocky high-country trail, you can be out there two to three hours or more on a single carry. That is a long time to be rationing water or running out of food. Leave every aid station with enough fluid and calories to comfortably reach the next one, plus a margin, and do not assume the next one is close.

Plan your drop bags around the longer carries and the cold (the race typically allows drop bags at stations like Long Park, Pool Table, Stone Cellar, Bowers, and Cathedral). Stash night layers, backup lights, and food you actually want to eat at hour 20.

The night, the cold, and the late-race lows

Most people are out for the better part of a day and a half, which means a full night above treeline, and late August up here gets cold fast. Nights drop below freezing, snow is a real possibility, and the race requires an emergency poncho or blanket, an extra layer, gloves and a hat, and two light sources for exactly this reason. The cold plus the altitude plus the hours is where the late-race lows live. The fix is boring and it works: keep eating, keep drinking, layer up before you get cold instead of after, and keep your feet moving through the dark patch.

Days are a different problem. The west side of the range runs hot, dry, and desert-like in the sun, so you can cook in the afternoon and freeze at night in the same race. Pack for both and manage the swing.

Pace by grade and effort, not by the watch

Your flat-ground pace is meaningless on these climbs, and it is doubly meaningless at 11,000 or 12,000 feet. What matters is grade-adjusted effort: hold a steady, conversational output you can keep all day, hike the steep pitches without guilt, and let the downhills come to you instead of hammering rocky descents early. The classic blow-up here is going out feeling great in the first thirty miles and paying for it through the cold night. Use a grade-adjusted pace to turn your real fitness into honest climbing and descending targets so you do not torch the first half.

Build a vert-aware, altitude-honest finish window

Do not predict your Rio Grande finish off a road 100 or a low-altitude trail time. The 18,700 feet of vert, the thin air, the technical footing, and the long aid gaps all add real hours. Build a vert-aware finish prediction for this course, then work it backward into the 36-hour cutoff and the aid-station cutoffs so you actually know how much buffer you have at each checkpoint. Out here, knowing your time budget between remote aid stations is the difference between a smart day and a panicked one.

Carbs: steady, trained, and altitude-proof

For a 100 miler this long, aim for somewhere around 60 to 90 grams of carbohydrate per hour, and only push the high end if your gut is trained for it. Altitude is the catch: thin air kills your appetite and slows your stomach, so the easy mid-race mistake is quietly under-eating until you bonk in the cold. Lean on liquid calories and simple, easy-to-swallow food when solids stop sounding good up high. Practice your exact race-day carb rate on long mountain runs so taking in food at altitude feels normal, not like a fight.

Sodium and fluid: carry for the gaps, not the next aid

Plan sodium around 300 to 700 milligrams per liter of fluid, pushing higher if you are a heavy or salty sweater, and remember the swing here: hot, dry, exposed sun in the day and freezing temps at night both mess with how much you drink. The bigger point is the carries. With long, remote stretches between aid stations, you have to leave each one with enough fluid and food to reach the next comfortably, with margin, instead of rationing 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.