Lake Sonoma 100K, 50K & Trail Sisters Half

Lake Sonoma 100K, 50K & Trail Sisters Half takes place on Saturday, April 10, 2027, around Lake Sonoma north of Healdsburg, California. Since 2026 the April weekend no longer hosts the original 50-miler: Trail Sisters, led by Gina Lucrezi, now directs a 100K, a 50K and a women-only half marathon. The 100K and 50K start and finish at the Lake Sonoma Visitor Center in Geyserville. The Trail Sisters Half is point to point from the Lone Rock parking lot, with a shuttle back from the finish and a 5-hour cutoff.

The 100K opens with the climb up Pritchett Peak and has 13 aid stations; a finish under 19 hours is a qualifier for the 2028 Western States 100. The 50K is billed as a first ultra and crosses the Lake Sonoma bridge near the finish. Entry fees rise in steps: $250, $165 and $95 (100K, 50K, half) through October 31, then $280, $185 and $110 through January 31, and $300, $200 and $115 through April 9, before processing fees. Looking for the original Lake Sonoma 50? It now runs in October as part of the Sonoma Fall Classic.