Lean Horse Ultra

JUL-AUG

31-1

2026

Run the scenic Lean Horse Ultra through the Black Hills from Custer on the gentle rails to trails George S. Mickelson Trail. Distances span 20 miles to a sanctioned 100 mile race with relay and team options on limestone.

31-1 Jul-Aug 2026

Custer, South Dakota

Website

100 miles 50 miles 30 miles 20 miles

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Event

The Lean Horse Ultra Marathon is an annual trail running event held in August in the Black Hills of South Dakota. The race was first run in 2005. The 100-mile event is a sanctioned 100-mile race and the organizer notes the event as a non-technical, scenic rails-to-trails course. The hosting town is Custer, South Dakota.

Course and conditions

The route follows the George S. Mickelson Trail and runs on a crushed limestone surface. The elevation profile consists of extended gentle climbs because the trail is on an old railroad bed. Average August daytime temperatures are listed as a high of 79 degrees and a low of 53 degrees. Visit the organization's website for the most recent information.