Union Pacific 3939, the final member of the batch of 25 4-6-6-4 Challengers that Alco built for the road in 1937, poses for a publicity photo with a dozen boxcars. UP’s first Challengers, 3900–3914, arrived in 1936.
Classic Trains coll.
UP Challenger 3939
By Angela Cotey | October 2, 2023
