The Union Pacific Challengers were a type of simple articulated 4-6-6-4 steam locomotive built by American Locomotive Company for the Union Pacific; 105 of these locomotives were built between 1936 and 1943. The Challengers were about 122 ft long and weighed 633,500 tons. Primarily in freight service, they operated over most of the Union Pacific system, however a few were assigned to passenger trains operating through mountain territory to California and Oregon. The locomotives were built specifically for UP and much of the experience gained later went into the design of the famous Big Boy. The technical breakthroughs achieved with the Challenger enabled the carrier to develop the Big Boy with the same speed expectations. Speeds in excess of 60 M.P.H., while unheard-of on other railroads using articulated steam locomotives, became commonplace on the Union Pacific.

        Challenger 3985 was built in July 1943 as fourth in its series. After 16 years in service, she spent the next 16 years stored in the Cheyenne roundhouse. After bring put on display for a short period of time, the approval was given in August 1979 to begin a complete restoration. By March 1981, she was back in operation.

       HO Scale model is a Broadway Limited Imports R4985 that has been converted to TCS WowSound and LED lighting. Cab detailed with crew figures.