The Big Alta
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Event details
The Big Alta is a three-day trail running event in Marin County, California, produced by Daybreak Racing and Freetrail. It takes place March 20-22, 2026 and is staged at Marinwood Community Center & Park (775 Miller Creek Road, San Rafael, CA). The event offers three race distances:
- 50K single loop
- 100K point-to-point
- 28K single loop
The courses summit many of Marin County’s highest points and include landmarks such as Loma Alta and Big Rock Ridge. Each race day has a participant limit of 300.
Logistics and registration
All registration is handled through Ultrasignup. Typical entry fees are:
- 100K: $300 - $330
- 50K: $175 - $195
- 28K: $140 - $155 Fees do not include applicable taxes or processing fees, and swag is extra.
Race services provided include course marking, chip timing and live on-course splits, staffed and stocked aid stations, professional medical support, bathrooms, radio communications, post-race food and beverages, custom finisher awards, and professional photography. Live tracking is provided by Ultralive and official results appear on Ultrasignup.
Logistics notes: a shuttle bus option for 100K runners is available for $20 to the Fort Baker start; runners should not drive and leave cars at the Fort Baker start due to National Park Service rules. Bib pickup, drop-bag requirements for 100K, curbside parking along Miller Creek Road, and a pet policy that allows leashed dogs at the staging area but not on course are specified. An inclement weather policy may activate a mandatory gear list, including a pack, rain jacket, phone, emergency blanket, whistle, ID, 400 calories of nutrition, 1 liter fluid capacity, and a hat or bandana. Visit the organization's website for the most recent information.