Mosquito Pass (13,185′), Mosquito Range

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.

StatsRoute DescriptionDirectionsNotes

Rating: Difficult
Road: CR 12
One Way: 17 miles / 27.5 km Alma to Leadville
Elevation: 10,361′ – 13.185′ / 3,158 m – 4,019 m

Take CR 12 from Alma off Hwy 9 if coming from the east side of the pass. Turn on CR 12 where the road gradually becomes more narrow, steep, and rocky as you near the summit. The road down to Leadville is also steep with large drop offs from the shelf road until you reach the lakes below.

A high-clearance, 4-wheel drive vehicle is recommended

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.





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