Lake Sonoma 100K

Lake Sonoma 100K & 50K Event

The event features three distances on April 11, 2026: the Lake Sonoma 100K, the Lake Sonoma 50K, and the Trail Sisters Women's Half Marathon. It takes place in Healdsburg, California, with the start/finish at the Lake Sonoma Visitor Center.

• Lake Sonoma 100K: A Western States qualifying course. It is described as "relentlessly hilly and remote" with 13 aid stations.
• Lake Sonoma 50K: A trail ultra with 6 aid stations.
• Trail Sisters Half Marathon: A women's half marathon starting at Lone Rock Trailhead.

All races are cupless; runners must carry their own bottle, flask, or bladder. Aid stations provide hydration and snacks. EMT services, live timing, music, and pizza are provided post-race.

Specific runner policies include no pacers allowed for any distance. For the 100K, crew access is permitted at specific aid stations, and drop bags are allowed at designated locations. A headlamp is required for 100K runners leaving a certain aid station after 3:30 PM.

Parking is at the Lake Sonoma Visitor Center lot for the 100K and 50K. For the Half Marathon, parking is at the start area with a shuttle back from the finish. Camping is permitted in the main lot on Friday and Saturday nights.

All finishers receive a custom gift. For the 100K and 50K, this is a bottle of wine or a non-alcoholic option. Half Marathon finishers receive a mug.

The organizer states there are no deferrals, credits, or transfers. A 50% refund is available for cancellations made on or before December 31st. Visit the organization's website for the most recent information.