Summit Marin's two highest peaks on a classic single-loop through iconic Bay Area trails
The Big Alta 50K takes place on March 20, 2026 in San Rafael, CA.
The Big Alta 50K is 31 miles with 6,700 ft of elevation gain.
No — The Big Alta 50K uses open registration; no lottery is required.
Yes, crew is allowed at The Big Alta 50K. Sign in to Trailrace to see crew access for each aid station.
No, pacers are not allowed at The Big Alta 50K.
Yes, The Big Alta 50K allows drop bags.
The Big Alta 50K has 3 aid stations along the course.
The overall cutoff for The Big Alta 50K is 8h30m. Per-aid-station cutoffs are available to signed-in Trailrace members.
Other trail races within 105 miles
The Big Alta 50K is a demanding single-loop trail race through the highest ridgelines of Marin County, combining long fire road climbs with sweeping singletrack descents and endless views across the San Francisco Bay Area. The course summits Loma Alta and Big Rock Ridge — the two highest points in Marin County — and weaves through oak woodlands, open grasslands, and wildflower meadows. At 31 miles with 6,700 feet of gain, this is a tough, inspiring race through some of the most beautiful terrain in Northern California.
Some ultra experience recommended
San Rafael, CA, United StatesMarch 20, 2026
| Location | Mile | Elevation |
|---|---|---|
START/FINISH - Marinwood Community Ctr Start | 0.0 | 79 ft |
Aid 1 - Fox Hollow Aid Station | 9.4 | 262 ft |
Aid 2 - Big Rock Aid Station | 14.3 | 656 ft |
Aid 3 - Chicken Shack Aid Station | 23.2 | 305 ft |
Finish Finish | 31.0 | 79 ft |
Sign in to see cutoffs, crew access, drop bags, and services for every aid station.
Friendly, leashed dogs are allowed at the event staging area and finish line, but not on the race course.
Late March in Marin County delivers variable spring conditions. Daytime highs reach 55-75°F with morning lows in the 40s°F. The course traverses exposed ridgelines where wind can be significant, and spring fog or rain showers are common. The 8AM start and 4:30PM cutoff keeps the race largely in daylight, but morning layers and rain gear are advisable.
Spring conditions can include sun, wind, fog, and rain showers in a single day
Exposed ridge running along Loma Alta and Big Rock Ridge can be windy
Spring rainy season — mandatory gear policy may be activated if rain is forecast
No required gear specified
No recommended gear specified
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