Ruth Anderson Memorial Endurance Run

Ruth Anderson Memorial Endurance Run is an ultramarathon held in San Francisco, California, circling Lake Merced. Runners complete a multi-lap course on a 4.475-mile paved bike path, with aid stations at the start/finish and each loop. The event features distances associated with a 50M designation, including time cutoffs after 7 and 10 laps, reaching roughly 31 to 45 miles; the history also notes a 100k/50k distance in records.

The course offers USATF-certified maps and relies on a dedicated team of Race Directors and volunteers, with support from SF Rec & Parks and Tailwind Nutrition. The atmosphere is community-minded and historic, drawing steady annual participation since 1986. Visit the organization's website for the most recent information.