Lake Sonoma 100K

Event overview

The TERREX Lake Sonoma weekend takes place at Lake Sonoma near Healdsburg, California on April 11, 2026. The event offers three distance options:

• 100K
• 50K
• Trail Sisters Half Marathon (13.1 miles)

The 100K is a Western States qualifying course. The Trail Sisters race is a women’s only half marathon and uses a point-to-point out-and-back format that begins at Lone Rock and finishes at the Lake Sonoma Visitor Center.

Courses and support

Courses include long climbs (including Pritchett Peak), rolling singletrack, madrone groves, lake overlooks and a crossing of the Lake Sonoma bridge. Aid and support details: the event is cupless (runners must carry their own bottle or hydration system); aid stations are supplied with Skratch Labs products plus food and basic supplies; EMT services are provided on course. Specifics published for the 100K include 13 aid stations (8 full, 5 water-only), and for the 50K six aid stations (4 full, 2 water-only). Crew access and drop-bag locations are identified for each distance in the race information.

Practical information

Start and finish facilities are at the Lake Sonoma Visitor Center for the 100K and 50K; the half marathon starts at Lone Rock with a shuttle from the finish back to Lone Rock. Parking is provided at the Visitor Center lots and Lone Rock as noted. Vehicle and tent camping are allowed in the main lot on Friday and Saturday nights. All finishers receive a commemorative item and post-race refreshments. The event lists adidas TERREX as presenting partner. Visit the organization's website for the most recent information.