Lean Horse Ultra

JUL-AUG
31-1
2026
Run the scenic George S. Mickelson Trail in the Black Hills at the Lean Horse Ultra Marathon in Custer, South Dakota. Distances from 100 mile to 20 mile plus relays offer a limestone trail challenge for solo runners and teams.
31-1 Jul-Aug 2026
100 miles 50 miles 30 miles 20 miles

Always double-check with the organizer's website! This page may contain affiliate links.

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 and includes a sanctioned 100-mile event. Distances offered include:

  • 100 Mile
  • 100 Mile Relay (up to 5 runners)
  • 50 Mile
  • 30 Mile
  • 20 Mile
  • 30 Mile Black Hills CrossFit Edition (Singles, team of 3, team of 6)

The event takes place around the town of Custer, South Dakota.

Course and conditions

All races use the George S. Mickelson Trail, a rails-to-trails route with a crushed limestone surface. The trail follows an old railroad bed, which produces extended gentle climbs along the course. Typical August daytime temperatures listed for the area are a high of 79 degrees Fahrenheit and a low of 53 degrees Fahrenheit. The site lists the event as a sanctioned 100-mile race in the United States. Visit the organization's website for the most recent information.

100 mi
100 Mile
100 mi
100 Mile Relay (up to 5 Runners)
50 mi
50 Mile
30 mi
30 Mile
30 mi
30 Mile Black Hills Crossfit Edition
20 mi
20 Mile

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