New for 2026. Starts at the Lake Sonoma Visitor Center, a short road section then rolling singletrack past South Lake, Island View, Warm Springs, Wulfow, Liberty Glen and Bummer, crossing the lake bridge before a downhill finish.
Punchy, relentless up-and-down; long gaps between aid, up to 6.9 miles between Warm Springs and Wulfow. Save energy for the last few miles: a screaming downhill after the lake bridge leads to the finish.
A Western States 100 qualifying 100K, paired with a 50K and the women's Trail Sisters Half Marathon, on singletrack above Lake Sonoma in Sonoma County wine country. The 100K climbs Pritchett Peak for a sunrise summit, drops to the Lake Sonoma Visitor Center, then runs an out-and-back on the original Lake Sonoma 50 Mile course to a turnaround at Lone Rock.
Founded 2008 as the Lake Sonoma 50 Miler by John Medinger and Lisa Henson. New race directors Gina Lucrezi and Justin Keller (Trail Sisters) took over in 2022. The Trail Sisters Half Marathon was added in 2023, alongside a move of the start/finish to the Lake Sonoma Visitor Center and a cash purse for the 50 Mile. Through 2025 the spring event was still 50 Mile + Marathon + Trail Sisters Half. For the 2026 edition, a separate fall race then called the California Fall Classic 100K (also a WSER qualifier) moved to April and was rebranded the TERREX Lake Sonoma 100K; a new 50K was added; the 50 Mile and Marathon distances were dropped from the spring lineup and moved to become the 'OG LS50' inside a new October race, the Sonoma Fall Classic, run by Aravaipa Running with founder Tropical John Medinger. See _meta.notes for the full account and the parts of this history that conflict across the organiser's own pages.
| Mile | Station | Cutoff | Crew | Bag | Pacer | Med | To next |
|---|---|---|---|---|---|---|---|
| 0.00 | Start | ? | ? | ? | ? | ? | 2.40 |
| 2.40 | South Lake | ? | · | · | ? | ? | 4.60 |
| 7.00 | Island View | ? | · | · | ? | ? | 6.90 |
| 13.90 | Warm Springs | 12:30pm | · | ● | ? | ? | 5.40 |
| 19.30 | Wulfow | ? | · | · | ? | ? | 2.70 |
| 22.00 | Liberty Glen | 3:15pm | ● | ● | ? | ? | 5.80 |
| 27.80 | Bummer | ? | · | · | ? | ? | 3.30 |
| 31.10 | Finish | 6:30pm | ? | ? | ? | ? | ? |
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