Lean Horse Ultra
Custer, United States • 31-1 Jul-Aug 2026
Lean Horse Ultra
The Lean Horse Ultra is a multi-distance trail running event on the George S. Mickelson Trail in the Black Hills of South Dakota. The event for 2026 is scheduled for July 31 to August 1. It is held annually in August and was first run in 2005. The hosting town is Custer, South Dakota.
The trail surface is crushed limestone and follows an old railroad bed, producing extended gentle climbs in the elevation profile. Average daytime August temperatures for the area are listed as a high of 79 degrees and a low of 53 degrees. The event is described as a non-technical rails-to-trails course and as a scenic rails-to-trails route. The 100-mile distance is noted as the 33rd sanctioned 100-mile race in the United States.
Event distances include:
- 100 Mile
- 100 Mile Relay up to 5 runners
- 50 Mile
- 30 Mile
- 20 Mile
- 30 Mile Black Hills CrossFit Edition with singles and team options of 3 or 6
The program includes individual races and relay formats. The course information emphasizes trail surface, elevation character, and local climate averages relevant to participants. Visit the organization's website for the most recent information.