Sean O’Brien Trail Runs Calabasas, CA   Jan 31, 2026

Message from Race Director Keira Henninger:
The Sean O’Brien 50k/30k/26M was created after the original Ray Miller course had suffered a devastating fire in early May. The area was badly burned, and in my opinion needed time to heal. I was inspired to still bring a solid, competitive, and tough 50 mile/50k race to southern California in early winter. I also had a deep desire to still have this sort of race in the beautiful Santa Monica Mountains.

The result was the creation of one of the most epic race courses to date on the West Coast. Personally mapped out and created by my close friend, Sean O’Brien, it only seemed fair to name the race after him. The race course consists of beautiful single-track on the Backbone Trail and miles of sweeping ocean views. The backcountry trails of the Santa Monica Mountains are breathtaking and some parts rarely touched.

The 100k is a WS100 qualifier.

This will be a cupless race. No plastic! We will not have cups at the aid stations. You must be self sufficient and carry hydration.