33rd sanctioned 100-mile race in the United States
Known as one of United States's best non-technical courses
One of the most scenic rails to trails courses in the country

The Lean Horse Ultra Marathon, held on the Mickelson Trail in the Black Hills of South Dakota, features the following events: 100 Mile, 100 Mile Relay, 50 Mile, 30 Mile, 20 Mile, and 30 Mile Black Hills CrossFit Edition

July 30th – 31st 2027

RACE OVERVIEW

Early Pricing Opens October 1st 2026
Standard Pricing January 10th 2027
Late Pricing July 1st 2027

Registration Closes July 16th 2027

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, and a 20-mile race. The course is held on the George S. Mickelson Trail.

*30-Mile Black Hills CrossFit Edition Singles and relay teams of 3 or 6.

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

Learn about Custer, South Dakota

RACE OVERVIEW

*30-Mile Black Hills CrossFit Edition Singles and relay teams of 3 or 6.

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.