Big Alta 100K
- 2026216 finishers
Races
Big Alta 100K
Fort Baker under the Golden Gate to Marinwood. Twelve thousand seven hundred feet. Headlands. Tam. Big Rock Ridge. The greatest hits tour north of San Francisco.
62.5 mi+10,079 ft-10,016 ft17 hours16 ft to 2,375 fttech 6/10Checkpoints per race bookGolden Gate startTrans-MarinWestern States qualifierMarch
Distance62.5 mi
Gain+10,079 ft
Loss-10,016 ft
Altitude16 ft to 2,375 ft
Technicality6/10
Air45°F to 70°F
- Start16 ft
- High2,375 ft
- Low16 ft
- Finish79 ft
Field, 2026scraped
Starters271
Finish rate80%
Median13:25
Sub-24216
Geometryderived
Steepest drop1,155 ft-9.9% over 2.2 mi
Course records
Men8:18:28Kellen Blumberg
Women9:45:34Robyn Lesh
The cruxCardiac Hill to Stinson and the Big Rock Ridge climb late (near mile 41)
Course DNA
The Course
Big Alta 100K runs 62.5 mi through Marin County, California. +10,079 ft gain and -10,016 ft loss. Surfaces skew 55% singletrack / 40% fire road / 5% paved. Cardiac Hill to Stinson and the Big Rock Ridge climb late. High point near 2,375 ft. Low near 16 ft. March temps run 45°F to 70°F. The course rewards patience early and punishes rushed descents after mile 31.
The Work
Train for 10,079 feet of climbing across 62.5 mi. Back-to-back long runs on similar surfaces. Practice power-hiking grades above 15 percent. 17 hours total means limited margin: rehearse fueling every 45 to 60 minutes and downhill eccentric work weekly. Technicality 6/10. Build a block that simulates the crux near mile 41.
Kit
March in Marin County, California: plan for 45°F to 70°F. Mandatory shell if rain is in forecast. Headlamp with spare batteries if 17 hours pushes past dark. Poles help on sustained climbs above mile 16. Vest capacity for 2 liters minimum. Shoes matched to 55% singletrack: lugs for mud, rock plate if the course turns technical after mile 31.
Race Day
Hold effort through mile 16. The field often splits on the first big climb after mile 31. Cardiac Hill to Stinson and the Big Rock Ridge climb late near mile 41 is where time is won or lost. Walk the steep pinches. Run the flats and gentle downhills. Crew at major aids: socks, calories, ice if hot. Transitions under 5 minutes when possible. Final third is 21 miles of fatigue management. Finish with reserve for the last descent.
Results
Big Alta 100K finish lines.
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Sources (1)
- Field stats (2026): https://ultrasignup.com/results_event.aspx?did=130945