The Grand Slam of Ultramarathons is a set of four of the most presitigious 100 mile races contested in the United States, comprising the Western States 100 in California, the Vermont 100 Mile Endurance Run in Vermont, the Wasatch Front 100 Mile Endurance Run in Utah, and the Leadville Trail 100 in Colorado. A small number of people manage to complete all four in one Calendar year.
