62 miles of Marin's greatest hits, from the Golden Gate to the finish line
The Big Alta 100K takes place on March 21, 2026 in San Rafael, CA.
The Big Alta 100K is 62 miles with 12,750 ft of elevation gain.
No — The Big Alta 100K uses open registration; no lottery is required.
Yes, crew is allowed at The Big Alta 100K. Sign in to Trailrace to see crew access for each aid station.
No, pacers are not allowed at The Big Alta 100K.
Yes, The Big Alta 100K allows drop bags.
The Big Alta 100K has 9 aid stations along the course.
The overall cutoff for The Big Alta 100K is 17h. Per-aid-station cutoffs are available to signed-in Trailrace members.
Other trail races within 105 miles
The Big Alta 100K is a world-class point-to-point trail race traversing the entire length of Marin County from Fort Baker near the Golden Gate Bridge to the finish at Marinwood Community Center. The course strings together Marin's greatest scenic landmarks — Fort Baker, Marin Headlands, Stinson Beach, Mount Tamalpais, Lagunitas Lake, Pine Mountain, Loma Alta, and Big Rock Ridge — into 62 miles of varied terrain including singletrack, fire roads, and exposed ridgelines. With 12,750 feet of climbing and a 17-hour cutoff, the race demands endurance and navigation savvy, with a mandatory GPS device required throughout due to high trail use in this National Parks Service-permitted region.
Experienced ultrarunners
San Rafael, CA, United StatesMarch 21, 2026
| Location | Mile | Elevation |
|---|---|---|
START - Fort Baker Start | 0.0 | 16 ft |
AS1 - Rodeo Beach Aid Station | 6.5 | 26 ft |
AS2 - Muir Beach Aid Station | 12.3 | 13 ft |
AS3 - Cardiac Hill Aid Station | 19.2 | 1,365 ft |
AS4 - Stinson Aid Station | 22.1 | 52 ft |
AS5 - Tam Summit Aid Station | 30.1 | 2,343 ft |
AS6 - Lagunitas Aid Station | 35.6 | 728 ft |
AS7 - Azalea Hill Aid Station | 38.8 | 1,083 ft |
AS8 - Fox Hollow Aid Station | 47.9 | 259 ft |
AS9 - Big Rock Aid Station | 52.6 | 656 ft |
FINISH - Marinwood Community Ctr Finish | 61.2 | 79 ft |
Sign in to see cutoffs, crew access, drop bags, and services for every aid station.
Friendly, leashed dogs are allowed at the event staging area and finish line, but not on the race course.
Late March in coastal Marin County brings classic Northern California spring variability. Morning temperatures typically start in the 40s°F and climb to 55-75°F by afternoon. Marine fog and coastal overcast are common early in the day near Rodeo Beach, Muir Beach, and Stinson Beach. Spring weather is famously unpredictable — sun, wind, fog, and rain showers can all occur within a single day. The 17-hour cutoff means many finishers will be running in darkness, with evening temperatures dropping back to the 40s°F. Come prepared for the full range of coastal spring conditions.
Coastal Marin spring weather can include sun, wind, fog, and rain showers all in one day
Runners finishing near the 11PM cutoff will experience cold, dark conditions with temperatures dropping to the 40s°F
Exposed ridgelines on Marin Headlands, Mt. Tamalpais summit, and Big Rock Ridge can experience strong winds
Spring rainy season — mandatory gear policy may be activated if rain is forecast race week
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