Lake Sonoma 100K
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Event overview
The Lake Sonoma weekend takes place on Saturday, April 11, 2026, at Lake Sonoma Recreation Area near Geyserville, California. Three race distances are offered:
- 100K
- 50K
- Trail Sisters Half Marathon (13.1 miles)
The 100K is a Western States qualifier (finish under 19 hours for 2027 qualification). The Trail Sisters race is women-only and uses a point-to-point course starting at Lone Rock and finishing at the Lake Sonoma Visitor Center.
Race details and logistics
Courses feature steep climbs (including Pritchett Peak), out-and-back sections, madrone groves, lake overlooks, and a bridge crossing on the 50K and half marathon. Aid station support varies by distance: the 100K has 13 stations (8 full, 5 water-only), the 50K has 6 stations (4 full, 2 water-only), and the half has 3 stations. Races are cupless; runners must carry a bottle, flask, or bladder. Drop bag and crew access points differ by race (listed for Woodbridge, Warm Springs, Liberty Glen, Lone Rock, and South Lake). Pacers are not allowed.
On-site services include EMT coverage, live timing, stocked aid stations with Skratch Labs hydration and standard ultra fare, finish-line awards (custom wine bottle or non-alcoholic option for 100K and 50K; Trail Sisters finisher mug), parking in the Visitor Center lots, camping on Friday and Saturday nights, and a shuttle from the finish back to Lone Rock for the half marathon. Registration opens October 1 and tiered pricing is published. Visit the organization's website for the most recent information.
