The Big Alta 100K

March 21, 2026

registration opens October 14th!
 
EVENT INFO
50K Race
28K race
PHOTOS
RESULTS
 

100K

Welcome to The Big Alta 100K, a truly spectacular point-to-point trail race immediately north of San Francisco. We originally dubbed this course concept “Trans-Marin” a few years ago because of its epic traverse of the Marin County region. The course packs a laundry list of “greatest hits” scenic highlight locations into 62 miles, including Fort Baker, the Golden Gate Bridge, Marin Headlands, Stinson Beach, Mt. Tamalpais east peak, Lagunitas Lake, Pine Mountain, Loma Alta, Big Rock Ridge and more!

The course is as challenging as it is scenic, amassing 12,750’ of vertical gain (same loss) on a mix of singletrack trail and California carpet fire roads, and great crew access to boot. We consider this course and the extensive permit approvals required to host this race as one of our greatest accomplishments… We can’t wait to share it with you!

Race Day Schedule

Saturday, March 21, 2026

  • Bib Pickup:

    • NO RACE MORNING BIB PICKUP available. All 100K runners must pick up their bibs Thursday, March 19 at SFRC Mill Valley or Friday, March 20 8AM-5PM at Marinwood Community Center staging area.

  • Shuttle Bus Pick Up: Load up at Marinwood Community Center at 3:50AM, buses depart by 4:00AM. Shuttle Bus is OPTIONAL. Runners may be dropped off at Start Line by crew/supporters.

  • Shuttle Drop Off: 4:30AM at Fort Baker

    • Runners may be dropped off by car at Fort Baker for the start AFTER 4:30AM. Do not arrive before 4:30AM due to National Park Service restrictions.

  • Race Start: 5:00AM at Fort Baker (mass start, no waves)

  • Awards Ceremony: 6:00PM

  • Finish Line Cut-Off: 10:00PM (17 hours). See chart below for on-course cutoffs.

Course Map

  • CLICK “Open in Caltopo” in the map to open in a new tab.

  • INTERACTIVE MAP: Click HERE for an interactive course map where you can change layers, zoom in and out, view elevation profile, etc.

  • GPX DATA: Click HERE for a .gpx data file of the course with elevation data included.

Elevation Change

Approximately 12,750' of ascent and 12,700' of descent. 

Aid Stations

There are 9 aid stations on the course, all staffed with experienced, enthusiastic volunteers plus professional medical personnel.

All Daybreak races are CUPLESS.

Be sure to bring your own cup for liquids at aid stations (or use your hydration supplies, such as bottles, bladder, etc.). 

Hydration and nutrition options included at all aid stations: Neversecond C30 gels and C30 sports drink (30g of carb and 200mg sodium per serving for gels and drink), water, soda, bananas, oranges, chips, PB&J sandwiches, and more. Later aid stations will include warm, savory options.

Crew & Spectators

Crew are allowed at the following locations:

  • Fort Baker Start Line Area

  • Rodeo Beach Aid Station #1

  • Stinson Aid Station #4

  • Lagunitas Aid Station #6

  • Fox Hollow Aid Station #8

  • Marinwood Community Center Finish Line Area

There is no crew/spectator access allowed at any other aid stations or area on course due to permit restrictions and parking limitations.

A CREW GUIDE will be posted here by February 2026 for reference, download and printing.

Drop Bags

Drop bags will be available at Aid Station #2, #4, #6 & #8.

LABEL: Drop bags MUST BE labeled with your name, race, bib number and aid station name in permanent marker and received by race staff at your check-in before 5PM Friday of race weekend.

SIZE: Drop bag size must be smaller than a 20L day bag (shoe box size), made of durable, water-resistant material and less than 5lbs. Bags that are too large or heavy will not be accepted and will not go the requested aid station. 

RETURN: Drop bags cannot be brought back to the Marinwood Community Center finish line area until AFTER the aid station closes.

CONTENTS: Do not store valuables in drop bags! This includes car keys, ID, phones, bank cards, anything expensive, etc. The race is not responsible for missing, damaged, lost or stolen drop bags or contents.

FORGOTTEN BAGS: Please note we do not ship or deliver forgotten drop bags. You can arrange to pick up forgotten drop bags from us if we have them.

Poles

Trekking poles are allowed.

Pacers

No pacers allowed.

Inclement Weather Equipment Policy

If we have wet/inclement weather on race day, we will have a gear requirement for all runners that will help keep them prepared for confronting all types of conditions and in the event of a health/safety incident, allow a runner to wait for rescue and extraction. If implemented, the gear requirement will be in place for the duration of the race from start to finish. Gear checks shall be in place at aid stations. Required gear will include: a running pack, waterproof rain jacket, smartphone with course info and means of contact by race staff, emergency blanket, whistle, 400 calories of nutrition, 1 liter capacity of fluids, hat or bandana, ID.

Course Detail

Overall, the course is very runnable, but there are some major climbs that will ensure much of the fun being had is the Type 2 variety :) Fortunately, this is Marin County, with its globally-renown natural beauty and scenery providing ample distraction, as well as opportunity for reflection and gratitude. Course surfaces are predominantly a mix of dirt fire roads and single track trail, with some gravel fire roads and a dash of pavement at the beginning and end of the course.

Start (Fort Baker) to Aid Station 1 (Rodeo Beach): 

6.7 miles. Start at Fort Baker in the Golden Gate National Recreation Area, departing almost immediately under the Golden Gate Bridge on the paved Fort Baker Bay Trail, cliumbing up and crossing Conzelman Rd to reach SCA Trail at 1.0 mile and follows SCA for 2 miles, then veers LEFT onto Rodeo Valley Trail for a 2 mile descent. The course veers LEFT briefly onto Bobcat trail, then LEFT again onto Miwok Trail for 0.5 mile, then crosses Bunker Road and veers RIGHT onto Lagoon Trail that parallels the road for 0.75 mile to Rodeo Beach for Aid Station 1. Crew Access available.

Aid Station 1 (Rodeo Beach) to Aid Station 2 (Muir Beach): 

5.9 miles. Runners depart Rodeo Beach on Coastal Trail for 1.7 miles of steady climbing, gaining the Hill 88/Wolf Ridge ridgeline, then turns sharply LEFT to stay on Coastal Trail at its junction with Wolf Ridge Trail, descending for a bit over a mile to cross Tennessee Valley trail. The course continues straight on Coastal Trail for 3 miles, climbing and descending through scenic Pirates Cove before a 0.75 mile descent into Muir Beach for Aid Station 2. Drop Bags available.

Aid Station 2 (Muir Beach) to Aid Station 3 (Cardiac Hill): 

7.2 miles. Leaving Muir Beach, the course follows Pacific Way road for 0.25 mile to Hwy 1. Runners cross the roadway only when safe to do so and with permission from course marshal onsite, then veer RIGHT onto Dias Ridge Trail for 2.7 scenic miles. The course then turns LEFT onto Miwok Trail for 1.6 miles before veering RIGHT onto Redwood Creek Trail briefly before reaching Muir Woods Rd. Runners STOP at the road crossing and wait for permission to cross. Leaving Muir Woods Road onto Deer Park Fire Rd for 0.5 mile before gaining the famous Dipsea Trail for 1.75 miles to reach Cardiac Hill for Aid Station 3.

Aid Station 3 (Cardiac Hill) to Aid Station 4 (Stinson):

3.0 miles. Departing Cardiac Hill, runners get a cruising descent for 2.9 miles on the Dipsea Trail to Highway 1, then follow the narrow highway shoulder for 50 meters, turning right onto Belvedere Ave in front of the Stinson Beach Fire Station to reach the Stinson Beach Community Center for Aid Station 4. Crew Access and Drop Bags available.

Aid Station 4 (Stinson) to Aid Station 5 (Tam Summit):

8.1 miles. This section is the crux of the race and the most challenging segment, with 3000’ of climbing over 8.1 miles. Runners depart Stinson aid station on Belvedere Ave heading east to reach the Matt Davis Trail for a 4 mile climb, offering spectacular views from the grassy meadows during the ascent. Runners reach Pantoll Road, then Runners STOP at the road crossing and wait for permission to cross. After the road crossing, running continue briefly on Matt Davis Trail, then veer LEFT very briefly onto Old Stage Rd, then turn LEFT onto Old Mine Trail, offering truly spectacular views for 1.0 mile, then veers RIGHT onto Mountain Theater fire road to reach the historic Mountain Theater. The course continues above the top of Mountain Theater on Rock Springs Trail for 1.5 miles, then veers LEFT onto Old Railroad Grade fire road for 1 mile, then turns RIGHT onto the little traveled Tavern Pump Trail for 0.3 miles, then a LEFT turn onto Fern Creek Trail for 0.4 miles and 500’ of climbing. Runners then turn RIGHT onto Old Railroad Grade for 200 meters to reach Tam Summit for Aid Station 5.

Aid Station 5 (Tam Summit) to Aid Station 6 (Lagunitas):

5.5 miles. Departing Tam aid station, runners veer RIGHT onto Verna Dunshee Trail for a stunning 360* half mile loop trip around the summit of Mt. Tamalpais, the highest point in Marin County, then turn RIGHT on the wood deck path past the Visitor Center, down a few steps then turns LEFT onto a little used tie trail for 200 meters to connect onto Eldridge Grade fire road for a 3.5 mile sweeping descent into the Mt. Tam Watershed. Leaving Eldridge Grade, the course veers LEFT onto Lakeview fire road for 1.25 miles to Lagunitas Lake for Lagunitas Aid Station 6. Crew Access and Drop Bags.

Aid Station 6 (Lagunitas) to Aid Station 7 (Azalea Hill):

3.2 miles. Leaving Lagunitas Aid Station, runners follow Shadyside Trail along the shoreline of Bon Tempe Lake, cross the Bon Tempe Dam Road to Bon Tempe Trailhead. The course turns LEFT on Bullfrog fire road for 0.25 miles, then turns LEFT over a footbridge onto Azalea Hill Trail for 1 mile to Azalea Hill Aid Station 7.

Aid Station 7 (Azalea Hill) to Aid Station 8 (Fox Hollow):

8.9 miles. After leaving Azalea Hill Aid Station, runners stop to wait for a safe time to cross Fairfax Bolinas Road, then follows Pine Mountain fire road for 1.7 miles. Continuing straight, the route becomes San Geronimo fire road for 1.5 miles before turning RIGHT onto White Hill fire road. The course follows the rolling White Hill fire road for 2.2 miles, then descends on the Porcupine Trail, then White Hill Trail for over a mile before going underneath Sir Francis Drake Blvd, then merging onto Old Railroad Grade fire road. Runners stick to Old Railroad Grade for 1.9 miles, then the short Fox Hollow Trail for .25 miles to reach Fox Hollow Aid Station. Crew Access and Drop Bags available.

Aid Station 8 (Fox Hollow) to Aid Station 9 (Big Rock):

4.8 miles. Runners depart Fox Hollow Aid Station on the Glen Fire Rd then Smith Ridge Fire Road for a steady 2 mile climb, pass through a cattle gate, then veer RIGHT onto Loma Alta Fired Rd as the course continues to climb, reaching the bald summit of Loma Alta. Savor the epic 360° summit views, followed by a steady 2.1 mile steady descent down to Big Rock Aid Station at mile 53.3.

Aid Station 9 (Big Rock) to Finish (Marinwood Community Center):

8.6 miles. Leaving Big Rock Aid Station, the course uses a pedestrian tunnel under Lucas Valley Road to connect onto the Big Rock Trail for a stout 3 mile, 1500’ ascent to gain the ridgeline of Big Rock Ridge, the second highest point in all of Marin County. The ridgeline offers 360° views of the entire San Francisco Bay Area and beyond. From the Big Rock Ridge summit near the radio towers, the course follows Big Rock Ridge Fire Rd on a gradual, rolling descent for 2 miles to the junction with Queenstone Fire Rd. Runners will veer RIGHT at this junction onto Queenstone Fire Rd, where the course drops along a big 2 mile descent, with sweeping views of Marinwood and the Lucas Valley below. At the bottom of Queenstone Fire Rd, runners pass a fire gate into the paved Marinwood neighborhood street of Queenstone Drive, cross Mill Creek Road at the cross walk, then turn RIGHT onto the sidewalk of Miller Creek Road for the final gradual half mile descent to Marinwood Community Park for the finish!

Cancellations

See the Daybreak Racing Cancellation Policy.