A point to point race the length of Marin County. It starts on the water at Fort Baker, goes under the Golden Gate Bridge in the first mile, and runs north through the Marin Headlands, Muir Beach, the Dipsea, Stinson Beach, the summit of Mt. Tamalpais, Lagunitas Lake, Pine Mountain, Loma Alta and Big Rock Ridge to the finish at Marinwood. There are nine aid stations, crew can reach four of them, and the clock runs 17 hours. Finishing the 2027 race under 17 hours is a qualifier for the 2028 Western States lottery.
The race calls the course very runnable, with some major climbs. The crux is the 8.3 miles out of Stinson Beach, which climbs 3,000 feet from the beach up Matt Davis Trail to the summit of Mt. Tamalpais. Underfoot it is mostly dirt fire road and singletrack, with some gravel fire road and a little pavement at the start and the end. Pine Mountain fire road, at around mile 40, is the rocky, technical stretch.
The Big Alta 100K runs the length of Marin County. It starts at Fort Baker, on the water at the north foot of the Golden Gate Bridge, and goes north for 62.5 miles and 12,750 feet of climbing through the Marin Headlands, Stinson Beach, the summit of Mt. Tamalpais, Lagunitas Lake, Pine Mountain, Loma Alta and Big Rock Ridge, finishing at Marinwood in San Rafael. It is mostly dirt fire road and singletrack, and the race is honest that it is very runnable with some big climbs in it. Freetrail and Daybreak Racing put it on in March, alongside a 50K and a 28K that start elsewhere on the same weekend, and the first running was in 2026.
The organisers had the course in mind for years before they had the permits for it, and called the idea Trans-Marin, for the way it traverses the county. The first running was in March 2026, two years after the 50K and 28K started the event. Finishing the 2027 race under 17 hours counts as a qualifier for the 2028 Western States lottery.
| Mile | Station | Cutoff | Crew access | Bag | Pacer | Med | To next |
|---|---|---|---|---|---|---|---|
| 0.00 | Start - Fort Baker | ? | ● | ? | ? | ? | 6.70 |
| 6.70 | Rodeo Beach | ? | ● | · | ? | ● | 5.90 |
| 12.60 | Muir Beach | ? | · | ● | ? | ● | 7.20 |
| 19.80 | Cardiac Hill | ? | · | · | ? | ● | 3.00 |
| 22.80 | Stinson | 12:00pm | ● | ● | ? | ● | 8.30 |
| 31.10 | Tam Summit | ? | · | · | ? | ● | 5.60 |
| 36.70 | Lagunitas | 4:00pm | ● | ● | ? | ● | 3.30 |
| 40.00 | Azalea Hill | ? | · | · | ? | ● | 9.10 |
| 49.10 | Fox Hollow | 7:00pm | ● | ● | ? | ● | 4.80 |
| 53.90 | Big Rock | 8:30pm | · | · | ? | ● | 8.60 |
| 62.50 | Finish - Marinwood Community Center | 11:00pm | ● | ? | ? | ● | ? |
START LINE - FORT BAKER. Google map: https://maps.app.goo.gl/TQUKMCLUX8JJq2hM9 . Parking: park only in designated gravel parking areas along the bayfront. Do not park on paved road shoulders, the Discovery Museum paved lot, Cavallo Point parking areas or Coast Guard parking areas.
Parking. Park only in the designated gravel parking areas along the bayfront. The paved road shoulders, the Discovery Museum lot, Cavallo Point and the Coast Guard lots are all off limits.
daybreakracing.comRODEO BEACH AID STATION #1. Drive time: 10 minutes if travelling from the start line at Fort Baker. Google map: https://maps.app.goo.gl/HQTykivnnQT35rUA9 . Parking: all crew parking is along Mitchell Road, head in only. Do not park in the paved day use parking area, per National Park Service requirements.
Parking. All crew parking is along Mitchell Road, head in only. The paved day use parking area is closed to crews by the National Park Service.
daybreakracing.comSTINSON BEACH AID STATION #4. Drive time: 40 to 45 minutes if travelling from Rodeo Beach. Google map to parking: https://maps.app.goo.gl/rpYHn9ovTfWxnNQu9 . Parking: all crew parking is down in the Golden Gate National Recreation Area Stinson Beach parking lots only, which open at 9 AM, then a short walk up to the aid station at Stinson Beach Community Center. There is no crew parking anywhere in the town of Stinson Beach or at the Community Center.
Parking. Crews park in the Golden Gate National Recreation Area lots at Stinson Beach, which open at 9 AM, then walk up to the Community Center. Parking in the town of Stinson Beach or at the Community Center itself is not allowed.
daybreakracing.comLAGUNITAS AID STATION #6. Drive time: 60 minutes if travelling from Stinson Beach. Google map: https://maps.app.goo.gl/yR5ZbSviSmh9LfQS6 . Parking: all crew parking is in the Lagunitas Lake day use picnic area parking stalls. Do not park along the entrance road, which is a fire lane. If the lot is full, either leave or park up in the gravel lot and walk to the picnic area. There is an $8 day use fee per vehicle. The automated pay station at the Sky Oaks Headquarters entrance kiosk takes credit cards and $1, $5 and $10 bills.
Parking. Crews park in the Lagunitas Lake day use picnic area stalls. The entrance road is a fire lane and cannot be parked on. There is an $8 day use fee per vehicle, paid at the Sky Oaks Headquarters kiosk, which takes cards and $1, $5 and $10 bills.
daybreakracing.comFOX HOLLOW AID STATION #8. Drive time: 15 to 20 minutes if travelling from Lagunitas. Google map: https://maps.app.goo.gl/Z9AdQqnxetECHJpk6 . Parking: all crew parking is along Glen Drive near the White Hill School. This is a quiet residential area, so be very respectful with parking and noise.
Parking. All crew parking is along Glen Drive near White Hill School. It is a quiet residential street, so the race asks crews to keep the noise and the parking respectful.
daybreakracing.comFINISH LINE - MARINWOOD COMMUNITY PARK. Drive time: 30 minutes if travelling from Fox Hollow aid station. Google map: https://maps.app.goo.gl/ahwzn6cD9n9a2QB4A . Parking: all crew parking is along Miller Creek Road curbside in Marinwood. This is a residential area, so be very respectful with parking and noise.
Parking. All crew parking is curbside along Miller Creek Road in Marinwood. It is a residential street.
daybreakracing.com8 people have been out there with a camera or a microphone.
These are other people's work and we link straight to them. Watching costs nothing and needs no account. More of them: every race we hold, on film.
Nobody sees it until we have read it. No account, no sign-in.
This changes nothing on the page on its own. Somebody checks it against the race first.
Somebody watches it before it goes anywhere near this page. What we are after is footage of this course, on the ground. If it would be just as true of any other race, it is not this.
We want the address of the file the race publishes, not the file. We download it from there so the page can say where the line came from.
We read every one of these and we write back. Every fact here carries the source it came from, and the way a wrong one gets fixed is a person checking it against what you tell us.
Cutoffs move, races get postponed, lotteries open and close. We read the race's own sources and record where every fact came from. Put your email in and we will send you what changed, and where we read it.
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What happens to your email. Nothing else. I do not sell it, and I will not send you anything except this race changing. One click gets you out.
I keep this catalog because the information is scattered and hard to trust. Telling you when it moves is the same job.
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