Lean Horse Ultra Marathon
Custer, SD
Fri, Jul 31, 2026
In 21 days · Fri, Jul 31, 2026
Don't let race day sneak up
One email during race week. That's it.
Friday, July 31st, 2026
560 Grunewaldt Dr, Custer SD
See race page
About this race
Registration Closes July 12th 2026!
RACE OVERVIEW
The Lean Horse Ultra Marathon is run in August every year in the Black Hills of South Dakota. It was first run in 2005. It features a 100-mile race, a 50-mile race, a 30-mile race, a 20-mile race, and a 30-mile Black Hills CrossFit Edition - Singles, 3, and 6 person relays. The course is held on the George S. Mickelson Trail.
Course Overview
Surface: Crushed Limestone
Course: Mickelson Trail
Elevation Profile: Extended gentle climbs. This is due to the fact the course is on an old railroad bed.
Hosting Town: Custer, South Dakota
Average August daytime temperature: High of 79 degrees. Low of 53 degrees.
Fun Facts
33rd sanctioned 100-mile race in the United States
Known as one of the best non technical courses in the United States
One of the most scenic rails to trails courses in the country
Course map
Suggested Races
Organize this race?
Claim it free to manage your listing — and get it featured for free, while spots last.