The Grand Slam of Ultra-Running is a prestigious challenge in the ultrarunning community that involves completing four of the oldest and most difficult 100-mile trail races in the United States within a single summer. This achievement is highly respected in the sport and tests the limits of endurance, mental fortitude, and physical resilience.

Races in the Grand Slam of Ultra-Running:

1. Old Dominion 100 Mile Endurance Run
   • Location: Woodstock, Virginia
   • Description: The Old Dominion 100, first held in 1979, is a classic ultramarathon that traverses the rugged terrain of Virginia's mountains. The race features a mix of gravel roads, single-track trails, and steep climbs, with 24 aid stations to support runners along the challenging course. Participants have 28 hours to complete the race, with those finishing in under 24 hours earning a sterling silver buckle.
   • Link: Old Dominion 100 Details
2. Western States 100 Mile Endurance Run
   • Location: Olympic Valley to Auburn, California
   • Description: Western States 100 is the world’s oldest 100-mile trail race, starting in 1974. This iconic race takes runners from the high-altitude start in Olympic Valley through the rugged Sierra Nevada mountains, with over 18,000 feet of elevation gain and 23,000 feet of descent. The course is known for its scenic beauty, difficult terrain, and extreme weather conditions.
   • Link: Western States 100 Details
3. Vermont 100 Endurance Race
   • Location: Killington, Vermont
   • Description: The Vermont 100 is one of the oldest 100-mile races in the U.S. and offers both a 100-mile run and a 100-kilometer option. The course takes participants through Vermont's picturesque countryside, featuring rolling hills, dirt roads, and forest trails. The race is unique in that it also includes a simultaneous horse race over the same course.
   • Link: Vermont 100 Endurance Race Details
4. Leadville Trail 100 Run
   • Location: Leadville, Colorado
   • Description: Known as the "Race Across the Sky," the Leadville Trail 100 is one of the most challenging ultramarathons at high altitudes in the Colorado Rockies. Runners must navigate 100 miles of rugged trails, including steep climbs and rocky terrain, all above 10,000 feet.
   • Link: Leadville Trail 100 Run Details
5. Wasatch Front 100 Mile Endurance Run
   • Location: Kaysville, Utah
   • Description: The Wasatch Front 100 is the final race in the Grand Slam series and is often considered the most challenging. The course winds through the Wasatch Mountains, with technical trails, steep climbs, and breathtaking scenery. The race is known for its difficulty, including extreme weather conditions and the rugged nature of the course.
   • Link: Wasatch Front 100 Details

Completing the Grand Slam of Ultra-Running is a remarkable accomplishment that requires physical endurance, strategic race planning, and mental toughness. Runners who finish the series earn significant respect and recognition in the ultrarunning community.​