The Big Alta
50K · 31M
Scheduled
Registration opens Monday, September 14 at 6:00 AM Pacific, on UltraSignup, under one event entry covering all three distances. Each distance has sold out earlier each year.
Race dateMarch 19-21, 2027
Duration3 days
Start7:00am
Whenin 191 days
First held2024
Free, and always will be. NavRun makes money from race-day planning for runners who want it, never from this.
Ultras change constantly, sometimes the morning of. Always confirm with the race director and the official website before you rely on anything here.
Distance
31M
Climb
6,700 ft
Descent
6,700 ft
High point
not checked yet
Time limit
9:00:00
Aid stations
5
Started
does not apply to this race
Finished
does not apply to this race
Finish rate
not checked yet
The course
Where it goes
loop · 5 aid stations · rust marks a stop your crew can reach
One loop out of Marinwood Park and back to it, 31 miles with about 6,700 feet of climbing. The route runs the ridges north of San Rafael: Spring Hill, the 680 Trail up the flank of Loma Alta, over the bald summit of Loma Alta at mile 12.2, down to Big Rock, then the three mile climb up Big Rock Ridge, the second highest point in Marin, and out over Chicken Shack and Ponti before dropping back into Marinwood. Three aid stations, crew at two of them, and nine hours on the clock.
The race calls the course very runnable with some long, stout climbs. Underfoot it is a mix of dirt double track fire road and singletrack, along ridgelines, down ravines and across open grassland and oak woodland, with some gravel fire road and a little pavement at the start and the end. The big one is the three mile, 1,500 foot climb from Big Rock up to the Big Rock Ridge summit.
The race
What this one is
The Big Alta is a March weekend of trail racing in Marin County, run out of Marinwood Community Center & Park in San Rafael. The 50K goes on the Friday, one loop of 31 miles and 6,700 feet of climbing over Loma Alta and Big Rock Ridge, on fire road and singletrack with the whole Bay Area laid out below. A 28K runs the same ground on the Sunday. Freetrail and Daybreak Racing produce it together, and the name comes off two of the summits the courses cross.
The first Big Alta was run in February 2024 with a 50K and a 28K, and moved to March the following year. In 2026 the event added a point-to-point 100K on the Saturday, which starts at Fort Baker in Sausalito rather than at Marinwood.
Getting in
Getting in
Entry, lottery and what the race asks of you before race day.
- Lottery
-
No
daybreakracing.com
- Lottery opens
-
does not apply to this race
daybreakracing.com
- Lottery draw
-
does not apply to this race
daybreakracing.com
- Field cap
-
350
daybreakracing.com
- Registration
-
UltraSignup
daybreakracing.com
- Qualifying
-
not checked yet
- Minimum age
-
not checked yet
- Transfers
-
No
daybreakracing.com
- Deferrals
-
No
daybreakracing.com
Running, crewing, pacing or still deciding
How NavRun helps with The Big Alta
Nine hours, and three stations with a clock on each.
You are running it
You reach Fox Hollow, mile 9.4, before its 9:25am cutoff, and you already knew that this morning.
An arrival time for all 3 stations, each next to its cutoff, worked out from your own training.
Start free →
You are crewing it
You park at Fox Hollow, and you are standing there when they come in.
One link from your runner, with the stop and the window they arrive in.
You are deciding
You find out The Big Alta is months of work away, not years, and you enter.
Put in a race you have already run. NavRun shows you where this one sits from where you are.
No account needed →
Crew access, pacers and drop bags
The rules that shape your day
Anything marked "not checked yet" is a gap in what we hold, never a no from the race.
- Crew allowed
-
Yes
daybreakracing.com
- Vehicles per runner
-
1
daybreakracing.com
- Pacers
-
No
daybreakracing.com
- Muling
-
not checked yet
- Drop bags
-
Yes
daybreakracing.com
- Cupless
-
Yes
daybreakracing.com
- Course marking
-
Fully Marked
daybreakracing.com
- Night running
-
not checked yet
- Dogs
-
Not allowed
daybreakracing.com
- Headphones
-
not checked yet
- Crew rules
-
A runner may take help only at a crew accessible aid station or in the start and finish area. For the 50K that means the start/finish, Fox Hollow and Chicken Shack. There is no crew or spectator access at Big Rock, where parking is very limited and parking there breaks the event's permit. One passenger vehicle per runner. Crews bring their own supplies rather than using the aid station's, and pack out their own rubbish.
daybreakracing.com
- Pacer rules
-
No pacers are allowed on the course at any time.
daybreakracing.com
- Drop bag rules
-
One drop bag stop: Big Rock, aid station 2 at mile 14.3. Bags go out from the start and come back to the finish area once the aid station closes and the sweepers are through, roughly 1:00 to 1:30 PM. Leave valuables out: no wallet, ID, phone or keys.
daybreakracing.com
- Cutoff philosophy
-
The race asks runners to respect the cutoffs for two reasons it names: safety, and keeping the day inside the schedule its permits allow. It is also explicit that a cutoff is the time you have to leave an aid station, not the time you have to reach it.
daybreakracing.com
Aid stations
Every stop, and what you get there
● yes · no ? nobody has checked – does not apply to this race
| Mile |
Station |
Cutoff |
Crew access |
Bag |
Pacer |
Med |
To next |
| 0.00 |
Start - Marinwood Park
|
? |
● |
? |
? |
? |
9.40 |
| 9.40 |
Fox Hollow
|
9:25am |
● |
· |
? |
● |
4.90 |
| 14.30 |
Big Rock
|
11:00am |
· |
● |
? |
● |
8.90 |
| 23.20 |
Chicken Shack
|
1:30pm |
● |
· |
? |
● |
7.80 |
| 31.00 |
Finish - Marinwood Park
|
4:00pm |
● |
? |
? |
● |
? |
Driving your crew
Getting your people there
3 stops with directions the race published.
Fox Hollow
mile 9.40
cutoff 9:25am
Fox Hollow Aid Station: https://maps.app.goo.gl/KHg2FDGZKLkRbH2j8 . All parking is curbside along Glen Drive. Be respectful of the neighbours when parking and keep speeds respectful.
Parking. All parking is curbside along Glen Drive. It is a residential street.
daybreakracing.com
Chicken Shack
mile 23.20
cutoff 1:30pm
Chicken Shack Aid Station: https://maps.app.goo.gl/ragBzPBe3Nk45Vyk6 . All parking is at the Park & Ride off Alameda del Prado, then a quarter mile walk up the paved Chicken Shack Fire Road, behind the gate, to the tennis courts. Do not block the fire gate at any time.
Parking. Crews park at the Park & Ride off Alameda del Prado and walk a quarter mile up Chicken Shack Fire Road to the aid station. The fire gate has to stay clear.
daybreakracing.com
Finish - Marinwood Park
mile 31.00
cutoff 4:00pm
Parking. All event participant parking is curbside along Miller Creek Road near Marinwood Community Center and Marinwood Park. Do not park on neighbourhood side streets or in the Marinwood Park parking lot, which is kept for the general public, race officials and volunteers.
Same race, other lines
Other distances and other years
What it looks like out there
Somebody has been out there with a camera
the tables say the climb is long. these say what long feels like.
10 people have been out there with a camera or a microphone.
+ 2 more.
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.
Add to this page
What you know
every one of these is read by a person before it changes anything
Ran this race? Tell the next runner what you know.
Nobody sees it until we have read it. No account, no sign-in.
See something wrong or out of date? Suggest an edit.
This changes nothing on the page on its own. Somebody checks it against the race first.
Seen a course preview or a film of this one? Send it over.
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.
Have the GPX? Send us the link.
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.
Are you the race director? Get in touch and we'll make it right.
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.
Where this came from.
Every fact on this page records its source and when we last checked it: 137 sources for this race. Hover a source link to read the sentence it came from.
51% of what we track for a course is filled in. The rest says "not checked yet" rather than guessing.
Ultras change. We will tell you when this one does.
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.
No account, and nothing to cancel.
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.
Running this one?
NavRun builds your pacing from your own training, then turns it into a plan your crew can follow: when to leave and where to park.
Start free
