Mosquito Pass connects the towns of Alma to the east and Leadville to the west. The pass is the highest cross-able vehicle pass in Colorado, with all the higher roads only being open one-way.
Any weather is treacherous year round on this high mountain pass and it is usually only open from late July to early September before conditions shut it down. It is difficult, steep, and very rocky.
Road: CR 12
One Way: 17 miles / 27.5 km Alma to Leadville
Elevation: 10,361′ – 13.185′ / 3,158 m – 4,019 m
Each June, hundreds of people run to the top of Mosquito Pass in the Leadville Trail Marathon and Heavy Half Marathon, part of the CenturyLink Leadville Race Series.
The top of the pass is the turnaround point for the 21-mile course of the Western Pack Burro Ass-ociation’s burro races, held the first weekend of August each year and part of the Leadville Boom Days heritage festival.