The 4-6-6-4 Challenger Type Steam Locomotive

The Challenger Type, an 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 developed for use by the Union Pacific the railroad would also go on to own the most Challengers, eventually rostering 105 of the steamers! The locomotive was one of the most technologically advanced of its kind with all roller bearings and tractive efforts near or exceeding 100,000 pounds. Sadly, however, like the Yellowstones the Challengers had an extremely short lifespan. Upon delivery of the UP�s first Challenger during the late summer of 1936 all were scrapped by 1960, operating less than twenty years on nine different railroads (some were barely ten years of age before being scrapped!).

The Challenger Type has its beginnings due to a need by the Union Pacific for a more powerful locomotive that could handle trains more efficiently over the stiff grades of the Wahsatch Mountain Range in western Utah. Working with the American Locomotive Company (Alco) the Union Pacific came up with the 4-6-6-4 wheel arrangement that proved to be a great blend of power and speed and worked well for the railroad. After the initial #3900 proved its worth the UP went on to purchase a total of 105 of the Challenger Type with 252 in all built.

Aside from the Union Pacific other owners of the Challenger Type included the Clinchfield; Delaware & Hudson; Denver & Rio Grande Western; Great Northern; Northern Pacific; GN and NP-controlled Spokane, Portland & Seattle; Western Maryland; and Western Pacific. As with the UP�s use of the locomotives, all nine other carriers used them in heavy drag service where grades were stiff. Most of the 252 Challenger Types built came from Alco although Baldwin chipped in with 27 of that total. The below chart breaks the units down by railroad, type, and number:

� Clinchfield: Class E1 (8), E2 (4), E3 (6) � 18

� Delaware & Hudson: Class J � 40

� Denver & Rio Grande Western: Class L-105 (15), L-97 (6) � 21

� Great Northern: Class Z-6 � 2

� Spokane, Portland & Seattle: Class Z-6 (6), Z-8 (2) � 12

� Union Pacific: Class CSA-1 (15), CSA-2 (25), 4664-3 (20), 4664-4 (25), 4664-5 (20) � 105

� Western Maryland: Class M-2 � 12

� Western Pacific: Class M-100 - 7

Of all the 252 Challengers built, astonishingly only two remain preserved, both of Union Pacific lineage, 3977 and 3985. However, while 3977 is now on display in North Platte, Nebraska 3985 is not only restored to operation it has also become one of the most famous steam locomotives worldwide. 3985 remains fully operational and has been on the UP roster since it was delivered by Alco in 1943.

Today, along with sister 844, a Northern Type steamer, they annually chug along the UP system on railroad excursions and other promotional events. To put it bluntly, they are a true sight to behold so if you have the opportunity I strongly recommend seeing one (or both) of these old girls in action, as large steam locomotives operating at-speed on main line railroads today is extremely rare (and we should all be thankful to Union Pacific for keeping these two beautiful and historic pieces of railroad equipment in tip-top shape for future generations to have the chance to witness what railroading was like prior to 1960).

For more information on the Challenger Type please click here to visit SteamLocomotive.com to learn much, much more about this steam locomotive.

Lastly, for more information on the Challenger Type consider one (or both) of the books below. Guide to North American Steam Locomotives by author George Drury includes nearly 500 pages of information on virtually all of the steam locomotive wheel arrangements and designs (including streamlined steamers) ever developed. The book is a great resource on steam locomotives and a fine reference tool; you should find it very useful.

Also, consider the book American Steam Locomotives from author Brian Solomon. While this publication does not include quite as much technical data as Guide to North American Steam Locomotives it is still a very good resource with lots of information and best of all, is loaded with photographs!

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