Hesperus Mountain is the highest summit of the La Plata Mountains range of the Rocky Mountains of North America. The prominent 13,237-foot thirteener is located in San Juan National Forest, 13.2 miles northeast by east of the Town of Mancos in Montezuma County, Colorado, United States. The summit of Hesperus Mountain is the highest point in Mon…Hesperus Mountain is the highest summit of the La Plata Mountains range of the Rocky Mountains of North America. The prominent 13,237-foot thirteener is located in San Juan National Forest, 13.2 miles northeast by east of the Town of Mancos in Montezuma County, Colorado, United States. The summit of Hesperus Mountain is the highest point in Montezuma County.