RailKing Premier Steam 4-6-6-4 Challenger w/Proto-Sound 3.0 & DCS Scale Wheels -- Union Pacific #3976 (2-Tone Gray, yellow Stripes)

The first Challengers were conceived in 1936 to replace the Union Pacific's fleet of three-cylinder 4-12-2s. With a 50 mph top speed, the 4-12-2s had been the road's primary fast freight engines when built in 1926. But a decade later they were considered slow and difficult to maintain. So American Locomotive Works (ALCO) was commissioned to build what became one of the most successful fleets of articulated engines on any railroad. Forty Challengers were built in the 1930s. The pressure of wartime traffic brought an order for 65 more of these 70 mph greyhounds in 1942-44, with improvements based on lessons learned from the UP's 4-8-8-4 Big Boys. In service, the Challengers often complemented the Big Boys, speeding traffic over less rugged territory and handing it over to the Big Boys for the passage over Utah's Wasatch Mountains. The Challengers were steam power at its zenith. They incorporated all the technology that represented super-power steam, including roller be