There's a reason they call it "The highway to the sky."

Trail Ridge Road, in Rocky Mountain National Park, is the highest continuously paved road in the National Park system, peaking at 12,183 feet. 

In just a matter of minutes on the road, passengers have already climbed nearly 4,000 feet in elevation along narrow, winding switchbacks. 

1938. View of automobiles on Trail Ridge Road in Rocky Mountain National Park, Colorado. Snow covers the ground. Mountains are in the distance.

Horace Albright, director of the National Park Service said in 1931 during the road's construction, "You will have the whole sweep of the Rockies before you in all directions."

He was right! And since that year, the 48-mile road stretching from RMNP's east side to Grad Lake on the west has escorted thousands of visitors exploring the park and its scenery. 

And since that time, crews have spent the late winter and early spring clearing mountains of snow from its pavement.

These photos from the Denver Public Library's Western History Collection show the road from its beginnings! 

Construction on Trail Ridge Road began in September, 1929, and did not finish until July, 1932. At the time, Fall River Road was the only thruway in the park, and it was unable to handle the high volume of visitors and vehicles traversing it. Frequent snowslides were a concern, too. 

During road construction, workers had only about 4 months of the year (mid-June to mid-October) to work with tractors, graders, horses and a gas-powered steam shovel to create the road.

At the peak of construction, 150 laborers toiled on the task.

1950-1970. A Chevrolet "Park Ranger" truck stops by snow banks on Trail Ridge Road in Rocky Mountain National Park, Larimer County, Colorado; storm clouds fill the sky. License plate reads: "U.S. Government I-48312."

Workers tried to maintain as much of the natural landscape as they could during construction. Tundra sod was placed on road banks, rock projections were kept as "scenic window frames" and rocks matching the surrounding lands were used to build the tock walls along the road. 

Eleven miles of the roadway crest above tree line, around 11,500 feet in elevation. The winding road, also known as Highway 34, has offered motorists spectacular views of the Rockies for nearly a century. 

1940-1950. View of a sedan on Trail Ridge Road in Rocky Mountain National Park, Larimer County, Colorado; license plate reads: "Colorado I-78994." Plowed snow and pine forest edges the road.

At the top, it's normally windy and 20 to 30 degrees colder than Estes Park or Grand Lake. That explains why the road closes each winter and remains unavailable to motorists until around Memorial Day, weather depending. 

In the spring, it takes 40 to 50 days to fully plow and clear the highway. 

Trail Ridge Road is one of ten America's Byways in Colorado and a nationally designated All American Road. 

As of this article's publishing, the road has been opened to pedestrians and bicyclists, but is still off-limits to cars until at least May.