Built in 1941 by the American Locomotive Company at a cost of $265,000.00. Number 4006 is one of 25 "Big Boys", the largest successful steam locomotives ever built, with a total weight of over 600 tons. It is 132' 9 1/4" long, carries 33 tons of coal and 25,000 gallons of water in its tender. It is a 4-8-8-4 (simple) articulated locomotive.
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BigBoy, the largest successful engine ever created, was not only a technological achievement and trophy piece, rather a necessity for the Union Pacific Railroad. Build for one purpose and one purpose alone: to pull large tonnage over the 1.55% continuous grade up Sherman Hill in the Wasatch mountain region just east of Ogden Utah. Before BigBoy, a helper service was required. This is where a smaller engine is coupled to a mainline freight to "help" it over the hill. The engine would then return to the bottom of the hill and await the next through train. Not only was this a slow process, but rather expensive. A new engine was needed, one that could pull a train up the hill unassisted. The UP Class 4000, 4-8-8-4 articulated BigBoy was the answer.
Alco Locomotive Works was commissioned to build the engine. Starting in 1941, 20 engines were built: #4000 to #4019, then again in 1944, 5 more were delivered #4020 to #4024. At 6PM on September the 5th, 1941, the first BigBoy, #4000, strode through the east end of the UP's Omaha yard. After testing and trials, 4000 was immediately put into active service. Mainly used during the peak season from July through November, the 4000s were used to take the massively heavy red balls over the Hill. The red balls are also known a PFEs, or Pacific Fruit Express Reefers, basically produce trains. Due to the heavy nature of these cars when fully loaded, prior to BigBoy, it wasn't unusual to see 2, 3 or even 4 engines struggling up Sherman Hill! Now, just one BigBoy and one engine crew was needed, saving the Union Pacific a lot of money.
BigBoy served as king of the hill for 21 years! Over those 21 years, his track record will ever be remembered by steam BUFFs around the world. Traveling an astonishing 1 million miles each (4016 had the lowest mileage at 1,016,124 and 4006 the highest at 1,064,625), they accumulated more service then most, fighting their way relentlessly up the grades every day. They reigned supreme over Sherman Hill until the summer or 1957. Normally, it was not uncommon to see anywhere from 3 to 6 BigBoys traveling from Cheyenne to Laramie everyday, all pulling separate trains.
The day came that all steam BUFFs refused to accept, September 4th, 1957, not a single BigBoy was dispatched west out of the Cheyenne yards. The year 1958 saw even less BigBoy revenue, in fact, it saw the last of the regularly scheduled trains over Sherman Hill being pulled by a Class 4000. That year, only 10 were called into service and saw constant use from late August to early October, the rest sat dormant in the RoundHouse and engine storage tracks in the Cheyenne Wyoming yards; waiting for a call that would never come. The last revenue freight pulled by a BigBoy was July of 1959. "The 10 that saw action are to be commended, though, for their spectacular show once again on the Hill. It was grand and glorious and a little sad, knowing this was the last. For the symbol had fallen and the prophets were right, over the great forty-eight steam was gone. One of this great race should be forever enshrined for posterity at the root of Sherman Hill." (Joe G. Collias, The Last of Steam). Most were then retired in 1961 after lying and waiting, the last one retired July of 1962. Until September of 1962, 4 were still in fully operational condition, sleeping in Cheyenne...
8 survive today.
~ from The JLS Railroad Website & BigBoy Information Center (
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Museum of Transportation website (
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