⏵ Course guide · Mt. Tamalpais mountain race
Inside Trail Racing's Muir Woods Mountain Challenge starts at Stinson Beach and immediately climbs about 2,000 feet up Willow Camp hill, then continues via the Coastal Trail, Matt Davis Trail, and the famous Dipsea Trail through Muir Woods to Cardiac Hill. I will walk you through the course first, then give you a pacing and fueling plan built for a steep, technical Mt. Tam day. There are free calculators along the way to dial in your own numbers.
These facts come from the official Inside Trail Racing event page. Check the current year details, cutoffs, and aid stations before you commit. Race logistics change year to year.
Every distance shares the same brutal opener, then the 10K peels off toward the beach while the Half and 30K push deeper into Mt. Tam and Muir Woods.
The race starts off with a bang, about 2,000 feet of climbing in just over 2 miles up the infamous Willow Camp hill. It sets the tone for the entire course and is worth respecting on race morning rather than treating as a warm-up.
Between heavy breaths on the climb, you get views of Stinson Beach and the Pacific Ocean along the ridge-line, tight singletrack of the Coastal Trail. The 10K then makes a breathtaking descent on the damp, twisting Matt Davis Trail back to the beach.
The Half and 30K head back up Mt. Tam via the Dipsea Trail, continuing for a gorgeous stretch through Muir Woods. Once you hit the Cardiac Hill summit, you bomb back down to Stinson Beach along the famous Dipsea Trail, with incredible views and harrowing steps on the way down.
With 2,000 feet of gain packed into the first 2-plus miles, going out too hard here has consequences for the rest of the course, whichever distance you run.
A grade-adjusted pace target built for a genuinely steep opening climb gives you an honest number for what is sustainable on Willow Camp, rather than pacing off how the climb feels in the first quarter mile before the grade fully kicks in.
The famous Dipsea Trail descent from Cardiac Hill back to Stinson Beach includes harrowing steps and technical footing. A vert-aware finish prediction, checked against the 6.5 hour cutoff, helps you judge whether you have room to run the descent under control rather than racing it recklessly on tired legs.
⏵ Free tools to pace this course
Mt. Tam in July can swing from coastal fog to direct sun, and the front-loaded climb burns through glycogen fast right when your race is just getting started.
Aim for roughly 45 to 75 grams of carbohydrate per hour on the 30K. It is tempting to focus entirely on breathing and footing during the Willow Camp climb, but skipping fuel in the first hour sets up a harder second half.
Sodium in the 300 to 700 mg per liter range covers most runners. Mt. Tam microclimates can shift fast, coastal fog at the start, direct sun higher up, so do not assume one condition for the whole race.
⏵ Build your fueling plan
Get a carb, sodium, fluid, and caffeine plan per hour built for your weight, your goal time, and a steep Mt. Tam 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 Mt. Tam course profile, and your projected splits for the Willow Camp climb and Dipsea descent. Summit Line reads your real training, builds a plan for steep technical climbing, and rehearses your fueling so race day is something you execute, not guess at.
It opens with a punch: about 2,000 feet of climbing in just over 2 miles up the infamous Willow Camp hill, right from the start. From there the 30K and Half continue up Mt. Tam via the Dipsea Trail through Muir Woods to the Cardiac Hill summit before descending back to Stinson Beach. Inside Trail Racing calls it "a true competition for event-experienced and novice mountain runners alike," but that opening climb sets a serious tone immediately.
The 30K carries about 5,100 feet of gain over 19.1 miles, the Half about 3,600 feet over 13.5 miles, and the 10K about 1,890 feet over 6.7 miles. All three distances share the same brutal opening: roughly 2,000 feet of climbing in the first 2-plus miles up Willow Camp hill, before the routes diverge.
A July date on Mt. Tam can mean anything from cool coastal fog to direct sun once you clear the tree line, and the steep early climb burns through glycogen fast. Aim for roughly 45 to 75 grams of carbohydrate per hour on the 30K, and sodium in the 300 to 700 mg per liter range. Because the whole race fits within a 6.5 hour window and finishes with a steep descent, save some capacity for careful footing on the way down rather than emptying the tank on the climb alone. Build your numbers with the free ultra fueling calculator before race day.
The Half Marathon and 30K both carry a 6.5 hour time limit, and all runners must be off the course by 2:00 PM regardless of their 7:30 AM start time. Given the steep, technical nature of the course, that window is tight enough to demand real fitness, not a token cutoff.
The vast majority of the course runs on technical dirt trails and fire roads, with long grinding hills, rocky and rooty descents, and steps. Inside Trail Racing calls it "a trail runner's dream," and the route touches Willow Camp hill, the Coastal Trail's ridge-line singletrack with Stinson Beach and Pacific Ocean views, the damp and twisting Matt Davis Trail, and the famous Dipsea Trail up to Cardiac Hill through Muir Woods.
The 10K is a reasonable entry point: it still includes the tough Willow Camp climb but returns to the beach via the Matt Davis Trail without tackling the full Dipsea-to-Cardiac Hill stretch. The Half and especially the 30K are a bigger step, with sustained technical climbing and descending that rewards real trail fitness. If you are new to steep Mt. Tam terrain, start with the 10K before committing to the longer distances.
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<a href="https://runsummitline.com/guides/muir-woods-mountain-challenge">The Muir Woods Mountain Challenge course guide</a>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.