On the cold, damp, rainy morning of May 8, 2019, Union Pacific Big Boy No. 4014 descends the Wasatch grade at Castle Rock, Utah. The locomotive leads the 150th anniversary of the Golden Spike special downgrade toward Echo Canyon, and the way steam shrouds the train, it appears that it is alone—no water cars, no 844 and no diesel—hauling Armour yellow passenger cars.