The San Juan Skyway is one of an All-American Road and a component in the Colorado Scenic and Historic Byway System. It forms a 233.0-mile (375.0 km) loop in the southwest part of the U.S. state of Colorado traversing the heart of the San Juan Mountains. It roughly parallels the routes of the narrow gauge railways: Rio Grande Southern (US 160, SH 145 and SH 62); and the unconnected Ouray and Silverton Branches of the Denver & Rio Grande along US 550 with the Silverton Railroad bridging a part of the gap. Its origin can be traced to the Around the Circle Route promoted by the D&RG.

From Ouray to Durango, the highway is referred to as the Million Dollar Highway. The first 7.0 miles (11.3 km) south of Ouray, the byway follows through the Uncompahgre Gorge. Just past the only tunnel on the route, just south of Ouray, the road crosses over Bear Creek Falls on a bridge at the location of an impassable toll booth on the original road. Before leaving the gorge, the byway passes through a snow shed under the Riverside Slide avalanche zone. A monument stands near here honoring those who have lost their lives in the avalanche, including several snowplow operators. At this point the byway enters Ironton Park, a nice flat valley in contrast to the gorge. The road ascends several switchbacks, or S-curves, past the Idarado mining operation to the 11,018-foot (3,358 m) summit of Red Mountain Pass, providing views of Red Mountain (Colorado) and several ghost towns. Back into the San Juan National Forest, the highway descends through the Chattanooga Valley to Silverton.

From Silverton, the byway passes over the 10,910-foot (3,330 m) Molas Pass and the 10,640-foot (3,240 m) Coal Bank Pass descending past the ski resort of Durango Mountain. From Hermosa, the road parallels the Durango and Silverton narrow gauge railroad before returning to Durango.

en.wikipedia.org/wiki/San_Juan_Skyway