The Y-3 offers model railroaders a unique opportunity: the chance to prototypically operate a massive Norfolk & Western articulated alongside Pennsy, Santa Fe, Union Pacific or Virginian equipment.
The story begins during World War I, when the U.S. government nationalized the railroads and the United States Railroad Administration (USRA) was charged with designing a series of standardized, government-issue locomotives. Conveniently, the Norfolk & Western Railway's delegate to the design committee for the USRA heavy articulated showed up with a full set of blueprints for his own road's Y-2 2-8-8-2. Happily, the N&W was already in the forefront of articulated design. The Y-2 used smaller cylinders and a higher boiler pressure than competitive engines, to provide higher freight speeds than the 20 mph maximum of traditonal articulateds of the time. Like most early 20th century articulateds, the Y-2 followed Anatole Mallet's original concept of using steam twice: supplying high pressure boiler steam to one set of drivers, and exhausting that steam into larger cylinders that drove the second set of drivers. (In later decades, supplying high pressure boiler steam to all four cylinders would become more common.)
And so the N&W's Y-2, with some improvements, became the prototype for the USRA 2-8-8-2. The government allocated 50 engines to the N&W, where they became class Y-3 when delivered in 1919 from Alco and Baldwin - too late to help with the war effort, but successful enough that the N&W ordered 30 more copies from Alco in 1923. As delivered, they sported eight-wheel tenders and twin cross-compound air pumps on the smokebox front. In the late 1920s, they were modernized with larger 12-wheel tenders and a Worthington feed water heater on the left side of the boiler; to balance the weight, the air pumps were moved to the right side of the boiler.
By the next World War, however, the Y-3 design was showing its age and the N&W was beginning to build its ultimate 2-8-8-2, the Y-6b. With other railroads in need of power for the war effort, the N&W sold off 19 of its Y-3 class. Six went to the Pennsylvania Railroad, where they became class HH1, working on drag freights between Hagerstown, MD and Harrisburg, PA during the war and later in Ohio until retirement in 1947-49. The Union Pacific bought five and used them for two years as class MC-57 in Wyoming. On the Santa Fe, eight Y-3s became helper engines on the Raton Pass through the Sangre de Cristo Mountains between Colorado and New Mexico. After the war, seven of the Santa Fe engines returned back east to again haul coal out of the Appalachians, this time for the Virginian Railway through the mid-1950s. The remaining N&W Y-3s, meanwhile, served out their later years in heavy switching and yard duty until retirement around 1958.