United States
Jan
31
Saturday
Sean O'Brien 100K
The Sean O'Brien event in Calabasas, California, offers multiple trail running distances including 100K, 50 miles, 50K, marathon, and 30K. The 100K race serves as a qualifier for the 2026 Western States 100. The course features scenic trail views with notable vantage points around miles 7 and 15, providing runners with beautiful natural surroundings.
This event is well-regarded for its challenging terrain and supportive atmosphere, attracting ultrarunners aiming for qualification and personal achievement. Registration closes mid-November, and the race takes place in late January, making it a key early-season trail running event. Visit the organization's website for the most recent information.
Always double-check with the organizer's website – things can change, and we might have sprinted past a few details!
100 km
100k
50 mi
50 Miler
50 km
50k
26 mi
26.2
30 km
30k
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