Ruth Anderson Memorial Endurance Run 2026

The Ruth Anderson Memorial Endurance Run is a looped ultramarathon held at the north end of Lake Merced in San Francisco. Race headquarters are located in the parking lot at the foot of Sunset Boulevard. Participants run a certified 4.5-mile loop around the lake, which is mostly flat with approximately 100 feet of elevation change per lap. The course consists mainly of a paved path, with a groomed dirt shoulder available for about 90% of the loop. The race setup is straightforward and suited for an endurance event. A full aid station is available each lap, allowing runners access to their vehicles and a place to store personal supplies near the aid area. A water fountain is also situated about halfway around the loop. This format allows runners to select their distance during the event, though they can only be scored for one distance. Upon reaching 50 km, runners must decide whether to finish at that distance or continue towards the 50-mile mark.