In the post World War I era, passenger schedules accelerated and the Union Pacific, like most U.S. railroads, completed its changeover from wood to steel passenger cars. So it was that the need arose for heavier passenger power on the Cheyenne, Wyoming to Ogden, Utah division, where the UP crossed the Continental Divide and the ruling grade was the notorious Sherman Hill. In late 1921, UP President Carl R. Gray wired his boss for authorization to have Alco develop a new 4-8-2 Mountain type for that route: "The development charges on this sample locomotive will approximate $25,000, all of which [Alco] will absorb and give us opportunity for a number of months to try out this locomotive in every kind of service and thoroughly develop and remedy any weaknesses before final order is placed. Will appreciate authority to do this."
Permission was granted, and the test engine, delivered in May, 1922, exceeded expectations, hauling 17 passenger cars over Sherman Hill - a job that had previously required double-headed Mikados. Over the next several years, the UP took delivery of forty 7000-class coal-burning and oil-burning 4-8-2s, as well as twenty 7850-class oil-burners for its Los Angeles and Salt Lake subsidiary. When the Depression put a damper on passenger bookings, surplus 7000s became standard power on the Omaha-Cheyenne route as well, displacing older Pacific types.
Like most steam engines, the 7000s and 7850s received improvements over the years. Larger tenders from 9000-class 4-12-2s were paired with some Mountains, while the main drivers on all sixty were replaced with Boxpok drivers in the late 1930s, after faster passenger schedules revealed a weakness in the original spoked drivers. Beginning in 1946, all 4-8-2s were repainted in the passenger service two-tone gray livery, which lasted until about 1952.
As the Mountains had replaced older power, so they too were eventually displaced by more powerful new engines, when the 800-class Northerns began to arrive in 1937. Some 4-8-2s were bumped to lesser routes while others were stored serviceable. World War II, however, granted the 7000s a reprieve, as they became valuable power for troop trains, helpers, extra sections, and even freight service. But the war ended and diesels began to arrive en masse, the Mountains once again became surplus engines. The first of the group was retired in 1949. As assignments dwindled, some were demoted to freight and even mixed train runs. After more than three decades of service, the last Mountain left the UP roster in 1956.
New for 2010, the Union Pacific 4-8-2 joins the Premier lineup. Like the prototype in its heyday, this engine is ready to handle your heaviest passenger assignments over the toughest route on your railroad - or meander along a country route with a mixed train or local freight, as the Mountains did in their golden years.