⏵ Course guide · Prescott high country
The Sierra Prieta 50K climbs about 5,298 feet across a 30.77-mile loop through the Sierra Prieta mountains above Prescott, Arizona, taking in Thumb Butte, Quartz Mountain, and the Sierra Prieta Overlook. A strict cutoff pace, enforced at every aid station, means this course punishes a slow start as much as a hard climb. I will walk you through the course and the cutoff math first, then give you a pacing and fueling plan built for a hot, mountainous August day, plus free tools to dial in your own numbers.
These facts come from the official race manual and the UltraSignup registration page. Check the current year details, cutoffs, and aid stations before you commit. Race logistics change year to year.
Starting and finishing at the White Rock Trailhead, the course loops through three prominent sections of the Sierra Prieta range: Thumb Butte, Quartz Mountain, and the Sierra Prieta Overlook, climbing between an elevation range of 5,697 and 7,094 feet for about 5,298 feet of total gain.
Big Juniper sits at mile 6.1, Quartz Mountain at mile 14.3, and Cattle Guard at mile 23.4. All three allow drop bags, and your Big Juniper bag gets moved to Cattle Guard once you pass through, so you effectively get two drop points across the course. Crew can reach all three aid stations, but only on foot or bike; no crew vehicles are allowed at any aid station.
The minimum pace is 2.56 mph, 23.37 minutes per mile, and the official race manual is blunt about it: "zero exceptions, and extremely strict." The cutoff times are when you need to have LEFT each aid station, not just arrived. If you reach an aid station before the cutoff but have not left by that time, you will be pulled.
The entire course is marked with pink flags, but the organizers explicitly anticipate some course tampering given how heavily used these trails are. Every runner is required to carry a cell phone with the race directors' numbers, plus a GPS-capable watch or phone with the course loaded, so you can navigate if markings disappear.
With aid-station cutoffs enforced on when you LEAVE, not just when you arrive, the margin for error on this course is thinner than a simple overall time limit would suggest.
The 8:23 AM cutoff at Big Juniper (mile 6.1) from a 6:00 AM start gives you 2 hours 23 minutes for the first 6.1 miles, close to the 2.56 mph minimum. A grade-adjusted pace target for this early climbing section helps you build real buffer before the terrain gets harder later on.
The mid-course cutoffs, 11:34 AM at Quartz Mountain (mile 14.3) and 3:07 PM at Cattle Guard (mile 23.4), are your real checkpoints for whether the day is going to plan. A vert-aware finish prediction, updated at each aid station, tells you honestly whether you have room to ease off or need to pick up the pace before the next enforced cutoff.
⏵ Free tools to pace this course
August in Arizona is hot and falls in monsoon season, with the official race manual warning of likely afternoon showers and lightning, so plan your fueling and gear around a day that can shift fast.
Aim for roughly 60 to 90 grams of carbohydrate per hour. Open Fuel provides drink mix at all three aid stations, and drop bags are allowed at Big Juniper, Quartz Mountain, and Cattle Guard (with your Big Juniper bag moved to Cattle Guard once you pass), so use those three touchpoints to keep your intake steady across the full 12-hour window.
Sodium in the 300 to 700 mg per liter range covers most runners here, leaning higher as the desert heat builds through the day. The race manual specifically recommends mid and back-of-pack runners carry a rain fly given how likely afternoon monsoon showers are.
⏵ Build your fueling plan
Get a carb, sodium, fluid, and caffeine plan per hour built for your weight, your goal time, and a hot Prescott August day 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 Sierra Prieta climbing profile, and your projected aid-station splits. Summit Line reads your real training, builds a plan for mountain climbing under a strict cutoff, and rehearses your fueling so race day is something you execute, not guess at.
This is a genuinely mountainous 50K, not a flat loop that happens to be long. The official race manual, GPX-derived, lists 30.77 miles with 5,298 feet of gain, climbing between an elevation range of 5,697 to 7,094 feet through three named high-country sections: Thumb Butte, Quartz Mountain, and the Sierra Prieta Overlook. Add a strict cutoff pace, 2.56 mph, enforced at each of the three aid stations, and this course rewards honest pacing more than raw speed.
The official, GPX-derived race manual lists 5,298 feet of total gain (5,295 feet per the route profile chart) over 30.77 miles, with the course elevation ranging from 5,697 to 7,094 feet. Note that the UltraSignup summary text rounds this to "4,500 feet," but the race's own detailed manual with the CalTopo-derived profile is the more precise source, so this guide uses the manual's number.
August in Prescott is hot and falls in monsoon season, with the race manual warning that afternoon showers and lightning are likely, so a rain fly is recommended for mid or back-of-pack runners. Aim for roughly 60 to 90 grams of carbohydrate per hour, and keep sodium in the 300 to 700 mg per liter range, leaning higher as the day heats up. Open Fuel provides drink mix at all three aid stations, and drop bags are allowed at Big Juniper, Quartz Mountain, and Cattle Guard, so plan your intake around those three touchpoints. Build your numbers with the free ultra fueling calculator before race day.
The race manual is explicit and strict: the minimum pace is 2.56 mph, 23.37 minutes per mile, and that pace is enforced at each aid station, meaning you must have LEFT the aid station by the posted time, not just arrived before it. Per the official aid station chart, that works out to roughly 8:23 AM at Big Juniper (mile 6.1), 11:34 AM at Quartz Mountain (mile 14.3), and 3:07 PM at Cattle Guard (mile 23.4), with a 6:00 PM finish-line cutoff, a 12-hour overall window from the 6:00 AM start.
The course is a loop starting and finishing at the White Rock Trailhead, climbing through three prominent sections of the Sierra Prieta range: Thumb Butte, Quartz Mountain, and the Sierra Prieta Overlook. The entire course is marked with pink flags, and the race organizers explicitly warn that some trail sections may see tampering given the high-use nature of the area, so carrying a GPS device with the course loaded is required gear, not optional.
The mandatory gear (a cell phone with race director numbers, plus a GPS-capable device for the course), the strict enforced cutoff pace, and no pacers allowed make this a race that demands real self-sufficiency, not just fitness. With 5,298 feet of climbing over 30.77 miles at elevations up to 7,094 feet, first-time 50K runners should have solid mountain trail experience and comfort navigating with a phone or watch before taking this on.
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<a href="https://runsummitline.com/guides/sierra-prieta-50k">The Sierra Prieta 50K course guide</a><iframe src="https://runsummitline.com/embed/race/sierra-prieta-50k" style="width:100%;max-width:420px;height:180px;border:0;" loading="lazy" title="Sierra Prieta 50K 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.
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