Union Pacific designers created an entirely new class of articulated power in the early 1940s. The massive size and weight required eight axles per engine, while four-wheel pilot and trailing trucks were added front and rear. During construction at ALCO, an unknown worker chalked the name Big Boy on one of the new 4-8-8-4s and a legend was born. Delivered in the fall of 1941, locos #4000-4019 were soon handling an incredible volume of wartime traffic. To keep pace, five more (#4020-4024) were delivered in 1944. Big Boys remained in regular freight service into the late 1950s, and as some of the last big steam in regular service, caught the attention of railfans worldwide. Officially retired in 1962, several were preserved by museums to inspire a new generation of fans.
 
The model comes fully assembled and painted, and features blackened, fine-flanged wheels for operation on Code 70, 83 and 100 track, razor-sharp graphics, realistic matte finish and formed metal handrails.