Ray Miller 50/50
Dec 5Malibu, CA50 mi, 50K +1
50K, 8 weeks before race day, 17 mi away, registration open
At a glance
- Date
- Jan 30, 2027
- Location
- Calabasas, California
- Distances
- 100K, 50 mi, 50K, Marathon, 30K
- Registration
- Closed Nov 15, 2025, via ultrasignup.com
Listed from UltraSignup. Checked Oct 18, 2026.
Plan this race for free
Aid stations, cutoffs and pacing in one plan, with the timeline your crew follows. Crew invites and race-day updates come with a Race Pass.
Build my planAbout this race
The Sean O'Brien Trail Runs is a multi-distance trail race held at Malibu Creek State Park in Calabasas, CA, offering distances from 30K to 100K. The 100K is a qualifier for the Western States Endurance Run, and the 50 Mile is a Sterling Silver Ticket Race for Angeles Crest 100.
Key dates
Registration closes
Nov 15, 2025
Race day
Jan 30, 2027
Email me updates about Sean O'Brien 100K/50M/50K/26.2/30K
Registration openings and major changes, like a new date or a cancellation.
Entry transfers
Can't race, or need an entry? Post it here so nobody has to ask if it's still available.
Tune-up races
Over The Hill Track Club High Desert 50K & 30K
Dec 5Ridgecrest, CA50K, 30K +1
50K, 8 weeks before race day, 118 mi away
HOKA Pacific Trails California by UTMB
Nov 13Rancho San Fernado Rey, CA50K, 20K
50K, 11 weeks before race day, 69 mi away
Straight-line distance
Similar races
Will Rogers 24 Hour/12 Hours/6 Hour
Feb 27, 2027Pacific Palisades, CA100 mi, 24 hr +6
Also 100K, 11 mi from Sean O'Brien 100K/50M/50K/26.2/30K
Angeles Crest 100 Mile Endurance Run
Oct 2, 2027Altadena, CA100 mi, 100K
Also 100K, 34 mi from Sean O'Brien 100K/50M/50K/26.2/30K, lottery closes Oct 26
Island View - Endurance Run
Oct 24Goleta, CA100 mi, 100K +1
Also 100K, 83 mi from Sean O'Brien 100K/50M/50K/26.2/30K, registration open
Malibu Canyon Trail Races
Jun 5, 2027Malibu, CA100K, 50 mi +3
Also 100K, 19 mi from Sean O'Brien 100K/50M/50K/26.2/30K
Straight-line distance
More 100K Races in California
All 100K Races in CaliforniaIsland View - Endurance Run
Oct 24Goleta, CA100 mi, 100K +1
SoCalUltraTrail at Tejon Ranch
Feb 27, 2027Lebec, CA100K, 50K +2
Will Rogers 24 Hour/12 Hours/6 Hour
Feb 27, 2027Pacific Palisades, CA100 mi, 24 hr +6
Sycamore Canyon
Mar 6, 2027Poway, CA100K, 50K +1
Angeles Crest 100K
Mar 20, 2027Altadena, CA100K, Marathon
Lake Sonoma 100K, 50K & TS Half
Apr 10, 2027Healdsburg, CA100K, 50K +1
Leona Divide
Apr 17, 2027Lake Hughes, CA100 mi, 100K +3
The Canyons Endurance Runs™ by UTMB®
Apr 22, 2027Auburn, CA100 mi, 100K +2
Coyote Two Moon
Apr 30, 2027Ojai, CA100 mi, 100K
Sea to Sky
May 1, 2027Jenner, CA100K, 75K +2
Bishop High Sierra Ultras
May 22, 2027Bishop, CA100K, 50 mi +2
Malibu Canyon Trail Races
Jun 5, 2027Malibu, CA100K, 50 mi +3
Races Near Los Angeles
All races near Los AngelesNo Name Trail Races
Oct 24Agoura, CA50K, Half Marathon +1
Lasse Viren Trail Races
Jan 2, 2027Malibu, CA50K, 20K +2
Trail Half League by SoCalTrail
Nov 26Topanga, CA
Mulholland Under the Stars Trail Race
Nov 7Tarzana, CA10K, 5K
LA Turkey Trail
Nov 26Los Angeles, CAHalf Marathon, 10K +1
Backbone Trail Ultra
Sep 18, 2027Santa Monica Mountains, CA68 mi
Ray Miller 50/50
Dec 5Malibu, CA50 mi, 50K +1
Griffith Park Trail Marathon
Nov 21Los Angeles, CA50K, Marathon +3
January Races Nearby
All January racesAvalon Benefit 50 Mile/50K Run
Jan 9, 2027Avalon, CA50 mi, 50K
San Diego 50 & Trail Runs
Jan 9, 2027Escondido, CA50 mi, Marathon +4
La Cuesta Ranch Trail Run
Jan 23, 2027San Luis Obispo, CA30K, 20K +1
Calico Trail Run
Jan 24, 2027Yermo, CA50K, 30K
24HR "The Grind"
Jan 29, 2027Perris, CA24 hr
Race planning
Plan Sean O'Brien 100K/50M/50K/26.2/30K with Crewable
Build your aid station plan, organize your crew, and dial in your nutrition strategy. Everything you need to finish strong.
Build my planAre you the race director for Sean O'Brien 100K/50M/50K/26.2/30K?
Claim this race to manage registration, volunteers, and race day.