Lake Sonoma 100K
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Event overview
The TERREX Lake Sonoma event takes place on April 11, 2026, at Lake Sonoma Visitor Center near Geyserville / Healdsburg, California. The weekend includes three races: a Western States qualifying 100K, a 50K, and the Trail Sisters women's Half Marathon. The venue offers parking at the Visitor Center for the 100K and 50K, and Lone Rock parking for the half, with a shuttle from the finish back to Lone Rock. Vehicle and tent camping is permitted in the main lot on Friday and Saturday nights.
Courses and practical details
Distances:
- 100K
- 50K
- Trail Sisters Half Marathon
The 100K begins with a climb to Pritchett Peak, follows parts of the original Lake Sonoma out-and-back course, and includes multiple aid stations. The 50K starts near the Visitor Center, moves onto rolling singletrack, and crosses the Lake Sonoma bridge before a downhill finish. The Trail Sisters half is a women-only out-and-back that starts at Lone Rock and finishes at the Visitor Center with shuttle service to the start.
All races are cupless; runners must carry their own bottle or hydration system. Aid station counts and locations vary by distance. Drop bags and limited crew access are allowed at specified aid stations for the ultras. Finishers receive a custom bottled award (nonalcoholic option available) and post-race provisions. Airports commonly used are San Francisco International and Sacramento International. Registration details and fees follow the published schedule. Visit the organization's website for the most recent information.