From the Vault
Mountain Ranges
Introduction
One of the most distinctive features of Summit County is our beautiful mountains. Believe it or not, these mountains have changed tremendously, starting 300 million years ago when the earth began to form parts of the Rocky Mountains.
Postcard of the Ten Mile Range c. 1940s
This image shows a postcard of the Ten Mile Range, Breckenridge, Colorado, in the 1940s.
Photograph Courtesy of the Summit Historical Society Collections.
About 10 million years ago, what we know as the Rocky Mountains began their slow rise due to horizontal crustal compression; the pressure in the earth forced the mountains to rise while rivers of ice carved distinctive features on the landscape. While no glaciers remain in Summit County, ice, water, and gravity still sculpt the landscape. Rockslides, avalanches, mudslides, and snowmelt carry materials down a slope.

Construction of the Dillon Dam
This image shows the construction of the Dillon Dam with Buffalo Mountain in the background. This image shows where the Dillon Dam Road is today.
Photograph Courtesy of the Summit Historical Society Collections.
Summit County has three major mountain ranges: the Ten Mile Range, the Gore Range, and the Mosquito Range. The county ranges from 7,947 feet above sea level (Green Mountain Reservoir) to 14,270 feet (Grays Peak). At high-altitude living, residents of Summit County continue to experience long winters and warm summers, all while exploring these sleeping giants.

Grays Peak- 14,274 ft
This image shows Grays Peak- 14,274 ft.
Photograph Courtesy of the Summit Historical Society Collections; The Doug Pierce Collection.
As various peoples moved through Summit County, they all used the mountains to meet their needs. The Ute People traveled through the mountains in the Summer and Fall as hunting grounds and trading centers. The mountains were the economic stronghold for miners, locking the sought-after minerals inside them. Homesteaders used the timber on mountainsides to create a lucrative logging industry. And finally, increased tourism brought ski areas and resorts to the county.

Construction of The Eisenhower-Johnson Memorial Tunnel in September 1970
This image shows the construction of what is now the Eisenhower-Johnson Memorial Tunnel in September of 1970. This is the building on the west portal.
Photograph Courtesy of the Summit Historical Society Collections; The Ada and Einar Lundgren Digital Collection.
Infrastructure has also impacted the mountains: roadbeds, railroads, and the construction of major highways carved into mountainsides. For example, the Eisenhower Tunnel and the Dillon Dam required dynamite to blast through landscapes. These developments shifted what mountainsides looked like, including removing popular recreational spots like the Ski Jump Hill in Old Dillon.

Ten Mile Range c. 1972
This image shows a landscape of the Ten Mile Range looking up the valley towards Peak One c. 1972.
Photograph Courtesy of the Summit Historical Society Collections.
Today, the mountains continue to be the pinnacle of the Summit County lifestyle, serving as a reminder of the natural beauty in the world and a place of reflection. Since the settlement of the area, people have enjoyed the recreation and natural beauty of the mountain ranges.

Breckenridge in the 1960s from Gibson Hill
Photograph Courtesy of the Summit Historical Society Collections.

Einar Lundgren exploring Mayflower Gulch in the summer of 1969.
Photograph Courtesy of the Summit Historical Society Collections; Ada and Einar Lundgren Digital Collection.

G-Lift on Copper Mountain in the winter of 1983-1984.
Photograph Courtesy of the Summit Historical Society Collections.

People watching a ski jumper on Ski Jump Hill in Old Dillon.
Photograph Courtesy of the Summit Historical Society Collections.

Man Standing on Path Along Peak Eight Reservoir, Circa 1945.
Photograph Courtesy of the Summit Historical Society Collections.

A dog and a horse at a sign pointing towards Ten Mile Creek and Dillon.
Photograph Courtesy of the Summit Historical Society Collections; The Doug Pierce Collection.
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