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⏵ Course guide · Idaho ultra

City of Rocks Ultra Course Guide

The City of Rocks Ultra is a no-frills high-desert trail race out of Almo in southern Idaho, weaving through the granite spires of City of Rocks National Reserve and Castle Rocks State Park. It comes in a few flavors, an Ultra around 51 miles, an Extra around 32, and a marathon, and the trails are runnable crushed granite and sand more than rocky and technical. The real test is the sun: you are out in the open most of the day. I will walk you through the course first, then give you a pacing and fueling plan that fits the climbing and the heat, with free calculators along the way to dial in your own numbers.

⏵ At a glance

City of Rocks Ultra quick facts

Date
Late May / early June (Saturday). 2026 listed around May 30, confirm with the race.
Location
Almo, southern Idaho. City of Rocks National Reserve + Castle Rocks State Park
Distances
Ultra about 51 mi · Extra about 32 mi · Marathon about 27 mi (a Half is also offered)
Elevation
Starts near 5,355 ft, high point around 7,252 ft. Moderate-to-significant climbing that builds with distance
Start
Early, around 5:30 to 6:00 AM MDT (2025 went off at 6:00 AM)
Cutoff
Generous, no-frills event. Confirm the current overall and any intermediate cutoffs with the race
Format
Run alongside an equine endurance ride. Distance changes allowed before AND during the race
Qualifier
No Western States, Hardrock, or UTMB qualifier status listed by the race

These facts come from the official race listing, UltraSignup, and race calendars. The exact date, distances, start time, and any cutoffs move year to year, and this race even lets you change distances on the day, so check the current race-day details before you commit.

The course: where City of Rocks is won and lost

The longer distances loop and stack their way through City of Rocks National Reserve and Castle Rocks State Park, on a mix of singletrack, doubletrack jeep roads, cow paths, and packed dirt. You climb between roughly 5,355 feet and a 7,252-foot high point through sage and pinyon pine, mostly out in the open. The footing is forgiving. The exposure is not.

The footing: granite dust and sand, runnable but draining

Most of the trail underfoot is crushed granite dust and sand, not the ankle-snapping rock you get on an alpine course. That sounds like a gift, and on the firm sections it is, you can actually run here. But loose, sandy stretches quietly tax your legs all day, because soft ground steals a little push from every stride. So the smart move is to run the firm, packed parts and stay relaxed and patient through the soft sand instead of fighting it. Save the energy for the climbs and for late in the day.

You move through granite spires and high-desert terrain that is genuinely beautiful, and on the Ultra you get a loop through the Castle Rocks formations on top of the main reserve. Take a second to look up. Then get back to running your effort.

The climbs: moderate-to-significant, and they build with distance

You start near 5,355 feet and the high point sits up around 7,252 feet, so there is real vertical here, and the more distance you sign up for, the more of it you absorb. None of the climbing is technical, but high-desert climbs have a way of feeling longer than they look because there is no shade and no break from the sun while you grind up them. Hike the steep pitches with purpose and keep your effort even, do not let an early climb that feels easy talk you into spending too much.

The race does not publish an official total gain, so do not anchor your whole plan to a vert number you saw on some calendar. Pace the climbs by effort, get to the high country with legs in reserve, and you set yourself up for a strong back half instead of a death march.

Sun and exposure: this is the whole race

If there is one thing that decides your day at City of Rocks, it is the sun. The course is primarily in direct sun with very little shade, and late May into early June in southern Idaho can go from a cool start to a hot, dry, fully exposed afternoon. The sun is strong at this elevation, and on the 51-mile Ultra you are out in it for hours and hours. People who treat the heat as an afterthought blow up. People who plan for it finish strong.

Start the day already on top of your fluid and salt, cover up smartly (a hat, light long sleeves, and sunscreen beat raw skin baking for eight hours), and pour water on yourself at aid to keep your core temperature down. The aid is friendly but the gaps can be long and sun-baked, so carry enough fluid and calories to cover the stretch in front of you instead of counting on the next table being close.

The long Ultra: the late-race lows

On the 51-mile Ultra, the back third is its own event. By then your legs are sanded down from hours of soft footing, the sun has taken a toll, and the climbs you shrugged off in the morning feel twice as long. This is where a relaxed early effort and steady fueling pay you back, and where pushing the first half quietly wrecks you. Expect a low patch, plan to eat and drink through it, and keep moving in the heat.

The friendly format helps: this is a no-frills race run alongside an equine endurance ride, and you can change your distance before and even during the event. That is a real safety valve, not a failure. If the day turns on you, dropping to a shorter distance and finishing upright beats forcing a blow-up, so know that option is there before you start.

Pacing strategy for a hot, exposed high-desert ultra

With real climbing between 5,355 feet and a 7,252-foot high point and a whole lot of open sun, City of Rocks is about managing effort and heat, not hitting a pace chart. Run the climbs by feel, and let the firm, runnable footing on the flats and descents be where you make your time.

Pace the climbs by grade, not by the watch

Your flat-ground pace is meaningless on the high-desert climbs here. What matters is grade-adjusted effort, so hold a steady output you can sustain up the grade and hike the steep pitches without guilt. The classic high-desert mistake is running the early climbs too hard because the air feels cool and the footing is good, then unraveling once the sun comes up and the legs go soft. Use a grade-adjusted pace to turn your real fitness into honest climbing and cruising targets, and you will not torch the first half.

Build a finish prediction you can actually pace into

Do not guess your City of Rocks finish off a flat road time. The climbing, the soft sandy footing, and especially the heat all add real minutes, and on the 51-mile Ultra those minutes pile up. A finish prediction that accounts for the vert and the conditions gives you a realistic window and lets you build a sane pacing plan, so you know roughly where you should be through the day instead of flying blind in the sun.

⏵ Free tools to pace this course

  • Grade-adjusted pace calculator to turn your flat fitness into honest targets for the climbs and the runnable stretches in between.
  • Race-time calculator for a finish prediction that factors in the climbing, so you can plan your day and any cutoffs you confirm with the race.
  • Race-equivalent calculator to turn a recent race result into a City of Rocks goal you can actually hold in the heat.

Fueling strategy for the sun and the duration

Depending on your distance, you are out in the open for several hours up to a full long day, with strong high-elevation sun and aid gaps that can run long. That makes carbohydrate, sodium, and fluid every bit as important as your fitness.

Carbs: steady and trained

Aim for roughly 60 to 90 grams of carbohydrate per hour, and only push the higher end if your gut is trained for it. Heat kills your appetite and slows your stomach, so keep intake steady and easy to swallow instead of gambling on big late doses once you are already cooked. Practice your exact race-day carb rate on hot long runs so 80-plus grams an hour feels normal, not like an experiment you are running for the first time at mile 35.

Sodium and fluid: this is where the day is saved or lost

On a fully exposed high-desert course, your sodium and fluid plan matters as much as anything. Lean toward the high end on sodium, often around 500 to 700 milligrams per liter of fluid, and more if you are a heavy or salty sweater. Just as important, carry enough fluid to cover the long, sunny gaps between aid instead of rationing to the next table and arriving empty and behind. Weigh yourself before and after a hot long run to find your real sweat rate, then build the plan around your own number, not a generic one.

⏵ Build your fueling plan

Get a carb, sodium, fluid, and caffeine plan per hour built for your weight, your goal time, and the City of Rocks sun 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 City of Rocks course profile, and your projected splits. Summit Line reads your real training, builds a plan for the climbing and the heat, and rehearses your fueling so race day is something you execute, not guess at.

Start free →Explore the demo

City of Rocks Ultra FAQ

How hard is the City of Rocks Ultra?

It is a real high-desert mountain ultra, and the difficulty scales with the distance you pick. The footing is mostly crushed granite dust and sand on a mix of singletrack, doubletrack jeep roads, and packed dirt, so it is more runnable than a rocky alpine course, but the sun is the catch: you spend most of the day in the open with very little shade, climbing through sage and pinyon pine between about 5,355 feet and a 7,252-foot high point. The 51-mile Ultra is a long day on tired legs in the heat, the Extra and Marathon are friendlier but still ask for real climbing and sun management. None of it is technical in the scary sense, it is an exposure-and-endurance test more than a footwork test.

How much climbing is in the City of Rocks Ultra?

The race does not publish an official total vert figure, so I will not pretend to one. What is confirmed is that you start near 5,355 feet and the high point sits around 7,252 feet, with the climbing stacking up as the distance grows. Call it moderate-to-significant: more than a flat trail race, less than a brutal vertical grind, with the gain front-loaded into the bigger distances. Treat the elevation as something you pace by effort rather than a number you chase, and confirm the current course profile with the race before you build a plan around a specific gain.

How should I fuel for the City of Rocks Ultra?

Plan it as a hot, exposed, multi-hour effort, and that means fuel and fluid carry as much weight as fitness here. Most runners do well on roughly 60 to 90 grams of carbohydrate per hour, leaning to the higher end only if your gut is trained for it, with sodium that climbs with the heat (often the high end of 300 to 700 mg per liter of fluid). The single biggest mistake on a sun-baked high-desert course is under-drinking and falling behind on salt, so carry enough to cover the gaps between aid instead of rationing to the next table. Run your own numbers for your weight, goal time, and the forecast with the free ultra fueling calculator.

What are the cutoff times for the City of Rocks Ultra?

This is a friendly, no-frills event that runs in conjunction with an equine endurance ride, and it does not advertise a strict cutoff structure the way a big qualifier race does. In practice the time limits are generous, and the race even lets you change your distance before and during the event if your day is not going to plan. Because the published details are loose, confirm the current overall limit and any intermediate cutoffs directly with the race before you start, and do not assume a hard number.

What is the terrain and weather like at City of Rocks?

The trails are mostly crushed granite dust and sand, with a mixture of singletrack, doubletrack jeep trails, cow paths, groomed sections, and packed dirt road winding through the granite spires of City of Rocks National Reserve and Castle Rocks State Park. You move through high-desert sage and pinyon pine forest, but the course is primarily in direct sun with very little shade. Late May and early June in southern Idaho can swing from cool early starts to hot, dry, fully exposed afternoons, and the sun is strong at this elevation, so heat and sun management are a core part of the day, not an afterthought.

Is the City of Rocks Ultra a good first ultra?

It can be a great first ultra if you pick your distance honestly and respect the sun. The non-technical, runnable granite-and-sand footing and the relaxed, generous-cutoff vibe make it more forgiving than a rocky alpine race, and the Marathon or Extra are reasonable first big efforts for a prepared runner. The 51-mile Ultra is a much bigger ask and not a casual first hundred-k-ish day. Whatever you choose, train the climbs, rehearse fueling and hydration in the heat, and get time on your feet in the sun, and the friendly format gives most committed runners room to finish.

This guide is independent and for planning only. The course details, dates, distances, start times, and cutoffs 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.