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The Union Pacific Challengers were a class of 4-6-6-4 articulated steam locomotives built by the American Locomotive Company (ALCO) for the Union Pacific Railroad beginning in 1936. The locomotives featured a simple articulated design with two engine units sharing a single boiler, allowing them to n...
The Union Pacific Challenger 3985 is a preserved 4-6-6-4 articulated steam locomotive. Notable for its powerful design originally built for heavy freight hauling in the late 19th century, it remains one of the largest and most impressive locomotives of its type. The Challenger is now operated by the...
Clinchfield 676 is a 4-6-6-4 Challenger-type articulated steam locomotive used on the steep mountain grades of the Clinchfield Railroad in Appalachia.
