Geyserville, California · Trail
Official site ↗Lake Sonoma
An April 100K and 50K from the Lake Sonoma Visitor Center in Sonoma wine country, the 100K on the old Lake Sonoma 50 Miler out-and-back with 15,000 feet of climbing and a 19-hour limit.
Distances
100K
- Distance
- 100 km (62 mi)
- Vert gain
- 15,000 ft (4,600 m)
- Start
- 5:00 AM GMT-7
- Cutoff
- 19 hr
WSER 2028 qualifier (sub-19:00)
50K
- Distance
- 50 km (31 mi)
- Vert gain
- 5,700 ft (1,700 m)
- Start
- 7:30 AM GMT-7
- Cutoff
- 11 hr
| Distance | Vert gain | Start | Cutoff | Notes |
|---|---|---|---|---|
| 100 km (62 mi) | 15,000 ft (4,600 m) | 5:00 AM GMT-7 | 19 hr | WSER 2028 qualifier (sub-19:00) |
| 50 km (31 mi) | 5,700 ft (1,700 m) | 7:30 AM GMT-7 | 11 hr | — |
About
Lake Sonoma runs its ultras every April from the Visitor Center at Lake Sonoma, north of Healdsburg in Sonoma County: a 100K and a 50K, beside the Trail Sisters Half Marathon. The 100K climbs Pritchett Peak at sunrise and then runs the out-and-back of the original Lake Sonoma 50 Miler, the race founded here in 2008. The 50K takes in the same trails and crosses the lake bridge. Finishers are given a bottle of wine.
Trail Sisters owns and runs the event, with Gina Lucrezi and Justin Keller directing. The 100K moved here from the autumn California Fall Classic for 2026, when the 50K was new, and a 100K finish inside 19 hours is a Western States 100 qualifier.
Course
The 100K starts at 5 a.m., climbs Pritchett Peak, drops to the South Lake Trailhead and runs the old 50-mile out-and-back before returning to the Visitor Center: 100 km with 15,000 feet of climbing and a 19-hour limit, closing at midnight. The 50K starts at 7:30 a.m. from the green beside the Visitor Center and passes the South Lake, Island View, Warm Springs Creek, Wulfow, Liberty Glen and Bummer aid stations before crossing the lake bridge: 50 km with 5,700 feet and an 11-hour limit.
How to register
Entry is open registration on UltraSignup, with no lottery or qualifier, and fees rising in three tiers from September to April. Registration for April 10, 2027 is open and closes on April 9. Cancelling by December 31 brings a 50 percent refund, and the race allows no deferrals, credits or transfers other than for pregnancy.