100 mile races in Colorado

The 17 100 mile ultramarathons in Colorado, with each one's climb, cutoff and date. Every race links to its own page, where you can see how it fits the runner you are now.

Race	Distance	Where	Date	Climb	Cutoff
American Heroes Run	100 Miles	Longmont, CO	Sep 11, 2026	—	30.183 h
Run Rabbit Run 100	100 Mile	Steamboat Springs, CO	Sep 18, 2026	20,391 ft	36 h
Sangre de Cristo 100	100 Mile	Westcliffe, CO	Sep 26, 2026	20,000 ft	38 h
NoCo Urban Ultra and Relay	100 Miles	Greeley, CO	Apr 11, 2027	1,200 ft	30.5 h
The Great Divide Ultra 100 Mile	100 Mile	Divide, CO	Jun 5, 2027	16,071 ft	36 h
Mace’s Hideout 100	100 Miles	Beulah, CO	Jun 5, 2027	22,500 ft	36 h
Weld Your Mettle Running Festival	100 Miles	Windsor, CO	Jun 5, 2027	—	36 h
Hardrock Hundred Mile Endurance Run	100 Mile	Silverton, CO	Jul 9, 2027	33,441 ft	48 h
Silverheels 100	100 Mile	Como, CO	Jul 9, 2027	18,172 ft	38 h
Ouray 100 Mile Endurance Run	100 Mile	Ouray, CO	Jul 16, 2027	40,000 ft	52 h
High Lonesome 100	100 Mile	Nathrop, CO	Jul 23, 2027	23,500 ft	37 h
Creede 100	100 Miles	Creede, CO	Jul 24, 2027	20,822 ft	40.5 h
HighFive100	100 Miles	Lake City, CO	Aug 6, 2027	40,000 ft	48 h
San Juan Softie 100	100 Miles	Durango, CO	Aug 13, 2027	20,000 ft	38 h
Leadville Trail 100 Run	100 Mile	Leadville, CO	Aug 21, 2027	15,492 ft	30 h
Rio Grande 100	100 Miles	South Fork, CO	Aug 21, 2027	—	38.5 h
Front Range Ultra Dayze	100 Miles	Loveland, CO	Sep 2, 2027	—	109 h