Lean Horse Ultra / UltraSignup
Lean Horse 100
Custer, South Dakota, United States
30–31 Jul 2027
A fast, gentle 100 mile out-and-back on the crushed limestone Mickelson Trail in the Black Hills, from Custer, South Dakota, with about 5,900 ft of gain.
Train for this raceAbout
The Lean Horse Ultra Marathon has run since 2005 on the George S. Mickelson Trail, an old railroad bed through the Black Hills of South Dakota. Long, gentle climbs and a firm crushed limestone surface make it one of the more runnable hundreds in the US.
The weekend also has a 50 mile, 30 mile and 20 mile, plus a CrossFit edition and relays. Everything starts in Custer.
Distances
| Name | Distance | Gain | Loss | Vert / km | Min altitude | Max altitude | Start | Start location | Finish | Course | Cutoff | Terrain | Technicality | Aid stations | Badges | Entry fee |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Lean Horse 100 | 160.9 km | 1,794 m | — | 11.1 m/km | — | — | 30 Jul 2027 12:00 America/Denver | Custer YMCA, Custer | Custer, South Dakota | Out and back | 30 h | Mixed | — | — | — | — |
| Lean Horse 50 Mile | 80.5 km | 811 m | — | 10.1 m/km | — | — | 31 Jul 2027 05:00 America/Denver | Custer Football/Track Complex | Custer, South Dakota | Out and back | 16 h | Mixed | — | — | — | — |
Lean Horse 100 terrain notes
Crushed limestone rail trail with extended gentle climbs.
Lean Horse 50 Mile terrain notes
Crushed limestone rail trail.
Registration
- Status
- Open
Links
Notes
2027 registration opened Oct 1, 2026 and closes July 16, 2027.