The Big Alta
Lucas Valley-Marinwood, United States • 20-22 Mar 2026
Event details
The Big Alta is a three-day trail running event scheduled for March 20-22, 2026 in Marin County, California. The event is staged at Marinwood Community Center & Park in San Rafael. Courses summit multiple high points in Marin County and include views across the San Francisco Bay Area. The event namesake references course landmarks Loma Alta and Big Rock Ridge. Registration is handled through UltraSignup and each race day has a field limit of 300 runners. The 100K is not a Western States Endurance Run qualifier until its second running in 2027.
Race distances
- 50K single loop
- 100K point-to-point
- 28K single loop
Logistics and policies
Race services include chip timing, live on-course splits and results, shuttle buses for the 100K, stocked aid stations, professional medical support, staffed bathrooms, post-race food and beverages, custom finisher awards, and professional photography. There is no lottery; races can sell out and a waitlist is used when capacity is reached. Transfers between distances are allowed but transfers into a sold-out distance are not available. A limited number of entries are reserved for professional athletes subject to event policies. Dogs are allowed at the staging area on leash but are not allowed on course. If inclement weather is forecast, organizers may require specific gear such as a running pack, rain jacket, smartphone, emergency blanket, whistle, ID, minimum nutrition and fluid, and a hat or bandana. Visit the organization's website for the most recent information.