The Big Alta

MAR
20-22
2026
The Big Alta is a three day trail running event in Marin County March 20 to 22, 2026, offering 28K, 50K and 100K courses that climb Loma Alta and Big Rock Ridge. Expect rugged single loop and point to point terrain with sweeping Bay Area views.
100 kilometers 50 kilometers 28 kilometers

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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.

100 km
100k Race
50 km
50k Race
28 km
28k Race

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