percent grade and switchbacks along many sections; the result was one of the highest adhesion (non-cog) standard-gauge railroads ever constructed in North America. This corridor over Rollins Pass was always intended to be temporary until what would later become the Moffat Tunnel was constructed and opened; therefore this overmountain route was constructed with more cost-effective materials: using wooden trestles (made of all Oregon fir) instead of iron bridges or high fills and wyes instead of turntables. Construction of this route was exceptionally dangerous and deadly: in a single day, 60 Swedish workers were killed when a powder charge exploded prematurely during the construction of Needle's Eye Tunnel. Along this route were three tunnels: Tunnel #31 (the tunnel at Ladora), Tunnel #32 (Needle's Eye Tunnel), and Tunnel #33 (the Loop Tunnel at Riflesight Notch). All three tunnels today are either completely caved in or have had multiple partial cave-ins. Other notable landmarks on the route included the Riflesight Notch Loop, located at Spruce Mountain: a spiral or loop where trains crossed over a trestle, made a ~90 degree gradual turn to descend , and passed through Tunnel #33 underneath the trestle. A rail station, Corona, was established at the summit of the pass, with a red brick and green roofed dining hall, weather station, power station, and lodging. In summers, the train ride from Denver to Corona was advertised as a trip, "from sultry heat to Colorado's north pole;" tourists could stand in snowdrifts in the middle of July or August. Tours launched from the Moffat Depot, a small building constructed in the Georgian Revival style, featuring two-story tall windows, intricate exterior brickwork, and roofline pommels. This building, located several city blocks northwest from Denver Union Station, was added to the National Register of Historic Places in 1976, and lay dormant for many decades after it was shuttered in 1947; in 2015, it was made the focal point of a senior living community center, after it was meticulously restored. Weather and operational difficulties Despite the fact that the line was enclosed in almost continuous snowsheds (wooden tunnels) near the summit of the pass, trains were often stranded for several days (and in some cases up to 30–60 days) during heavy snowstorms because snow could fall or be blown through the wood planking of the sheds. Delays affected the timeliness of both newspaper and postal mail deliveries. Coal smoke and toxic gasses