4-6-6-4

The Challengers were articulated design (meaning that either one, or both sets of driving wheels pivots to better and more safely negotiate curves), was one of the most successful large steam locomotive designs ever developed. Originally conceived for use by the Union Pacific in an attempt to create a more powerful steamer that could pull loads faster over stiff grades the railroad would also go on to own the most Challengers, eventually rostering 105 of the steamers.
The 4-6-6-4 was one of the most technologically advanced of its kind with advancements that allowed for both high horsepower and efficient operations. Sadly, however, like the Yellowstones the Challengers had an extremely short lifespan. Upon delivery of the UP’s first Challenger during the mid-1930s all were scrapped in short order, operating less than twenty years on nine different railroads (some were barely ten years of age).
The Challengers were built for 8 different railroads in North America including: Union Pacific, Western Maryland, Western Pacific, Clinchfield, Delaware & Hudson, Denver & Rio Grande Western, Great Northern, Northern Pacific, and Spokane, Portland & Seattle.
The unit's first test was to run an eastbound freight from Ogden, Utah to Green River, Wyoming where it would be forced to battle the Wasatch Range. To see just what the new 4-6-6-4 could do officials decided to run it unassisted for the round-trip and the locomotive more than proved its worth.
Of all the 252 Challengers built, astonishingly only two remain preserved; Union Pacific No. 3985 and Union Pacific No. 3977.
==Trivia==
*A former tender from Delaware & Hudson #1508 remains and it's the only remaing tender from the Challenger of the Delaware & Hudson.
*Challengers were most common in the Union Pacific Railroad and the Clinchfield Railroad.
*There are decent numbers of challengers built for the Northern Pacific as the Z-6 through Z-8 class.
==Gallery==
* Images
Category:Steam locomotives
Category:Tender locomotives
Category:American locomotives
Category:Articulated locomotives
Category:4-6-6-4 locomotives
Category:4-6-6-4 steam locomotives
Category:Six-coupled locomotives
Category:Union Pacific locomotives
Category:Great Northern (US) locomotives
Category:Western Pacific locomotives
Category:SP&S locomotives
Category:Rio Grande locomotives
Category:Northern Pacific locomotives
Category:Locomotives
Category:American steam locomotives
Category:Standard gauge locomotives
Category:Wheel arrangements