A big part of settling the West was road building. A simple enough undertaking on the flatlands, the precipitous terrain of the Rocky Mountains presented much bigger engineering challenges. Shortening the way between destinations often meant traversing dizzying cliffs and plunging depths that dwelt side by side - and to produce an even roadway with a manageable grade became an almost Olympian competition of engineering ingenuity.
Our first image is of the "Otto Mears Toll Road ," named after the "Pathfinder of the San Juans," Otto Mears. Mears built hundreds of miles of toll roads in the rough terrain of the young state of Colorado, and the 12 mile section of U.S. Route 550 over 11,000 foot Red Mountain Pass, connecting the mining towns of Silverton and Ouray, is his most well known achievement. As you can see in this William Henry Jackson  photo, the "Million Dollar Highway" is characterized by steep cliffs, narrow lanes, and a lack of guardrails [to this day] for the narrow pathway cut directly into the side of the mountain.
Railroad routes required even more difficult solutions to the up and down topography, and to accommodate the gentle grades and curves needed, tunnels and in this case, trestles, were employed to get the job done. Another of Jackson's photos shows a Union Pacific Railway Company train on a high trestle bridge over Dale Creek  in Albany County, Wyoming.
Next is a Harry H. Buckwalter  photo of the Ouray Stage Line , with passengers, crossing a wooden bridge on the Million Dollar Highway in the 1890s. One wonders at the trusting nature of the passengers - perhaps if they saw the bridge they were crossing from this view they wouldn't be so comfortable. I myself would be tempted to get out and crawl...
Next, another William H. Jackson photo shows the Atlantic & Pacific Railroad trestle over Diablo Cañon  in Coconino County, Arizona. This is a steel and concrete structure, and the men posing on it are no doubt confident of their own handiwork, especially after probably hanging from it in harnesses to weld the thing together. It's a long way down - don't drop that screwdriver, Bill!
The mining industry drove many engineering innovations, and one of the commonly used technologies was the "flume." A flume is an elevated "gravity chute" for water - but the water is merely a vehicle for transporting other materials, namely, gold and silver ore. Though not a thrill for travelers, this "Flume on a Granite Wall " was probably pretty hair raising to build.
Next is a picture of the Montrose Placer Mining Company flume , in Montrose County, Colorado, during its construction in 1890. Perched 400 feet above the Dolores River, traces of this flume are still visible from Highway 141 heading down to Nucla. The gentleman posing at the railing must have had nerves of steel.
Once considered an engineering wonder of the world, the Devil’s Gate High Bridge  section of the Georgetown Loop is still functioning and serves as a tourist attraction in Georgetown, Colorado. Adding to its appeal is the fact that it's a narrow gauge route - a favorite subspecies to railroad buffs.
This spectacular stretch of track was completed in 1884 and connected the thriving mining towns of Georgetown and Silver Plume, only 2 miles apart in the steep, narrow canyon of Clear Creek. Engineers designed a corkscrew route that traveled nearly twice that distance to connect them, slowly gaining more than 600 feet in elevation. The route included horseshoe curves, grades of up to 4%, and four bridges across Clear Creek, including the massive Devil’s Gate High Bridge, towering 95 feet above the creek at the bottom.
Finally, we have an L.C. McClure  view of another of Otto Mears' routes, the Highline, Silverton Branch , near Rockwood in the Canyon of the Rio Los Animas (Animas Gorge), in La Plata County, Colorado. This is another narrow gauge route, and we see a Denver & Rio Grande Railway train with one freight and two passenger cars on a rocky cliff shelf high above the Animas River in about 1895.
Otto Mears built several railroads during his 91 years, including the Rio Grande Southern Railroad from Durango to Ridgway, the Silverton Railroad, and the Silverton Northern Railroad. From 1888 to 1892, Mears issued special railroad passes to dignitaries and friends to allow them to ride free on any of his lines. Some of these rare passes were made of silver or gold and are now highly prized collectors' items.
[Be sure to click the photos to the left for larger versions.]