Altitude Series: San Jacinto via Marion Mountain (~16.5mi/5,200ft)
Details
Join us for the next hike in our Altitude Series, a structured training track designed to build endurance, pacing, and elevation tolerance for larger mountain routes, including San Gorgonio, Mt. Whitney, and other high-altitude objectives.
This route climbs San Jacinto Peak (10,834 ft) from Marion Mountain through forested lower sections before connecting into alpine terrain near Little Round Valley and Wellman Divide. The ascent is steady and sustained, gaining elevation continuously before the final exposed push to the summit.
From the summit, we’ll descend via the Round Valley Loop, passing through high-elevation terrain and long stretches of alpine forest before returning to the trailhead.
Approximately 16.5 miles round trip with about 5,200 ft of elevation gain. Typical time 7 to 9 hours depending on pace and stops. Expect sustained climbing, extended time above 9,000 ft, exposed sections near the summit, and a long endurance-focused day at altitude.
Here’s the full activity from our recent Altitude Series benchmarks, including all splits and details, to give a clear sense of how each day flows:
[Altitude Series] Cucamonga Peak | Benchmark 1 | NSC | Hike | Strava
[Altitude Series] Mt. Baden-Powell | Benchmark 2 | NSC | Hike | Strava
[Altitude Series] Big Horn and Ontario Peak | Benchmark 3 | NSC | Hike | Strava
[Altitude Series] Mt. Baldy | Benchmark 4 | NSC | Hike | Strava
[Altitude Series] San Bernardino Peak | Benchmark 5 | NSC | Hike | Strava
Who This Hike Is Suited For:
- Hikers comfortable with 15+ mile routes
- Ability to sustain a steady climbing pace on long uphill terrain
- Ability to maintain continuous forward movement for 7–9 hours
- Experience fueling and hydrating during extended efforts
Group Size & Admission Policy: Group size is intentionally limited to maintain safety, cohesion, and steady mountain pacing on long, sustained routes.
All hikers will initially be placed on the waitlist. Admission is based on pace compatibility and experience with sustained elevation routes.
First-Time Participants (Altitude Series):
If you have not previously hiked with us on a comparable route, please message the organizer with:
1. Date of your most recent 15+ mile hike
2. Distance, elevation gain, and completion time
3. Your average moving pace
4. Comparable peaks or routes completed
Submission of this information does not guarantee admission. We intend to keep the group intentionally small and will admit hikers off the waitlist as space allows, based on overall pace compatibility and training alignment.
Trailhead: Marion Mountain Trailhead
Parking: Marion Mountain Trailhead parking area (Adventure Pass required). Parking is limited at the trailhead. There is a small dirt parking area across from the trailhead, with limited roadside parking nearby.
Essentials:
• Water (3.5-4L; electrolytes highly recommended)
• Snacks/fuel
• Hat, sunscreen, sunglasses
• Hiking poles (recommended, especially for the descent)
• Offline maps/navigation recommended
Note on Punctuality & RSVP: Please be on time — we’ll wait up to 5 minutes past the start. If you’re running late, you can post your ETA in the event discussion, but the group may still begin without you. If your plans change, please update your RSVP — it helps us know who to expect on the trail.
Disclaimer & Safety Notice: Not So Casual Hikes are challenging outings designed for hikers in strong shape who know their limits and show up prepared. Organizers are volunteers—not guides—and cannot be responsible for your pace, navigation, or safety. We hike at a steady pace and the group may spread out. Please be prepared to navigate independently if you fall behind, though we’ll aim to check in at major junctions when possible. By signing up, you accept full responsibility for your fitness, gear, hydration, and navigation, and agree to hold harmless the Organizer, Co-Organizer, Assistant Organizers, and fellow participants for any incidents or injuries. Participation also means you agree to Meetup’s Terms of Service. Hiking carries inherent risks, including trip/fall injuries, bee stings, poison oak, ticks, snakes, coyotes, or mountain lions. Be prepared for sun exposure, heat, or marine layer conditions depending on the day.