Expected October 2027
Distance
Climb
Start Time
Terrain
Ruth Anderson Memorial Endurance Run sends runners around a 4.475-mile loop of the Lake Merced bike path in San Francisco, a paved trail with dirt shoulders that repeats until each runner reaches their chosen distance of 100K, 50M or 50K. The start and finish sit at Lake Merced Blvd. and Sunset Blvd., where the single aid station sits and where friends and family can greet runners on every lap. Racing begins at 7:00 a.m., and the 50M field must reach 31.1 miles by 2:30 p.m. and 44.5 miles by 5:40 p.m. First held in 1986, the race is one of the oldest ultras in the United States, and its flat profile has produced age group records from under 20 up to 80 and over.
Fast, flat 4.475-mile loop around Lake Merced
Paved bike path with dirt shoulders
Aid station at the start and finish on every lap
USATF certified 50K and 50M courses
One of the oldest ultramarathons in the United States, first run in 1986
Age group records from under 20 through to 80 and over
Spectator friendly lapped course in San Francisco
Start / Finish
Race HQ at Lake Merced Blvd. & Sunset Blvd., San Francisco, CA (bib collection and start)
Same point as the start, Lake Merced Blvd. & Sunset Blvd., San Francisco, CA
Terrain
Route
Race Day
What you get
Chip timing
Chip timing provided by Wendell Doman of Coastal Trail Runs
USATF certified 50K and 50M courses
Race day registration available for $10 extra if the race is not full
On the day
Before you enter
Other questions
The race starts at 7:00 a.m. on Saturday, October 10, 2026 from the race HQ at Lake Merced Blvd. and Sunset Blvd. in San Francisco, California. The 100K, 50M and 50K all set off together.
The course is a 4.475-mile paved bike path loop around Lake Merced with dirt shoulders, repeated until your distance is complete. It is flat and fast, and there is one aid station per lap at the start and finish.
Yes. Both the 50K and the 50M have USATF certified course maps, and the links to those certificates are published on the race page.
The flat, lapped paved loop with an aid station every 4.475 miles makes the 50K a manageable first ultra, and the event has welcomed runners trying the distance for the first time. The 50M and 100K are longer days and call for more experience.
Yes. The loop format means friends and family can stay in one place at the start and finish area at Lake Merced Blvd. and Sunset Blvd. and see runners on every lap of their race.
Entry fee
Registration isn't open yet. We'll show pricing when the organiser confirms.San Francisco, USA
Expected October 2027
Provisional date, around Oct 9Are you the organiser of Ruth Anderson Memorial Endurance Run?
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