The History of the Big Boy

The Union Pacific Railroad (UP) 4000-class steam locomotive “Big Boy” is the world’s biggest and strongest steam locomotive , with the world’s only 2DD2 (4-8-8-4) axle arrangement, a gross weight of 507 t, and a total length of 40 m, including the tender. After receiving an order from the Union Pacific Railroad, the American Locomotive Company (ALCO) constructed 25 Big Boys between 1941 and 1944, which were active until 1959. In 2019, a year that marks the 150th anniversary of the opening of North America's first transcontinental railroad, No. 4014 resumed operation after about 60 years of having been preserved in working condition.
The Union Pacific Railroad, which was founded in 1869 to be in charge of the construction of North America's first transcontinental railroad, manages a rail line network whose focus is the transcontinental route that runs from Omaha, Nebraska in the Midwest through Salt Lake City, Utah, and splits in two to arrive in Portland, Oregon and Los Angeles, California at the west coast. It is the oldest among all of the USA’s transcontinental routes and prides itself in having transported the largest volume of goods as the main railroad that connected to all important cities of the west coast during its time.
The most perilous pass for this line is the Wasatch Range in the Rocky Mountains, located at the border of Wyoming and Utah. This section of the line has an incline that reaches 11.4‰ and goes on for over 100 km. Although it is not so steep, the over 100 km long uphill incline was menacing to locomotives that had to pull over 1.6 km long huge freight trains.


The Union Pacific Railroad set up a locomotive of great size for this section early on. In 1936, the 3900-class “Challenger”, a simple articulated locomotive, also nicknamed the Big Boy’s “Big Brother”, was introduced. Although the Challenger was powerful and capable of high-speed performance, it was not enough to pull all trains by itself when crossing the Wasatch Range, which is why double heading was often necessary.


Building the Worlds Biggest Steam Locomotive

In 1940, World War II had already come to a boil in the West. Due to a rising demand in military transport, William Jeffers, the president of the Union Pacific Railroad, sensed the need to reinforce transportation capacities even further. Thus, he ordered Otto Jabelmann, vice-president and leader of the research and development department, to develop “a steam locomotive that possesses the ability to pull 3300 t heavy freight trains across the Wasatch Range on its own.” To achieve this, an enormous locomotive called a “2DD2” (4-8-8-4) that was equipped with a huge boiler and firebox and included two units of running gear between the leading truck and the trailing truck was designed.


In November 1940, UP ordered 15 of these locomotives from the American Locomotive Company. In January of the next year, 5 more were added to the order for a total of 20 locomotives for the first run, which was completed between August and October of 1941. They were given the numbers 4000-4019. Each of them cost about 265,000 per locomotive, which corresponds to about 4,200,000 today.


In 1944, transportation capacities increased rapidly and 5 more locomotives (No. 4020-4029) were added. This group, which constitutes the second run, had no cooling tube on the handrail deck and instead had adopted a mechanical cooling system. Furthermore, there were differences in the weight because different metals were used. In 1946, the first diesel locomotive for the Wasatch Range was introduced, and after 1948, operations between Ogden and Green River decreased, with the activity steadily moving towards the east. Because the cost for coal and labor had risen after World War II, the times had changed from favoring steam to diesel locomotives. Still, the Big Boy was one of the steam locomotives that kept running until the very end.


On July 21, 1959, the 18 ye...