Where did those exotic names for US steam loco types come from?

Written by: TrainSim-James

As Union Pacific Big Boy 4014 begins its historic journey back to Cheyenne, Mike Rennie (a British steam enthusiast, loco builder and tutorial writer) takes a look at the naming of US steam loco types.

“Where did those exotic names for US steam loco types come from?” That’s a question I asked myself when I first began to get interested in US steam locomotives. I already knew something about British steam locomotive types and classes, although it seems that on my side of the Atlantic, the types were nearly always referred to directly by their wheel arrangement (2-10-0, 2-8-0 and so on), with some exceptions, but names were apparently preferred only for the classes (different designs with the same wheel arrangement – for example, the “Britannia” class of Pacific). British Railways more or less standardised the practice of using numbers (the higher the number, the more powerful the locomotive) and letters (“P” for Passenger locomotives, “F” for Freight, “M” for mixed traffic), so that by the end of the mainline steam era in Britain, at the tail end of the 1960s, we were left with locomotives referred to with rather staid titles such as “BR Standard 9F” (although we have to be thankful that they didn’t completely stamp out the practice of bestowing names on individual examples – so we were lucky enough to witness the likes of “Evening Star”).

Now, when I read about steam locomotives in North America, names like “Mountain” and “Texas” jump off the page – they evoke images of the vastness of that continent and the huge distances that were covered. A few of those names were used for types in Britain too – “Prairie”, “Mogul” and “Pacific”. I wondered where those names came from. Did they originate in Britain, North America, or somewhere else? Here’s what I found.

First of all, and as a handy reference for anyone who, like me, is new to North American steam, here’s a list of names usually used to describe different types of wheel arrangement for rigid frame (that is, it doesn’t include articulated frames like the Big Boy) steam locomotives in the USA:

0-6-0 Six-wheel switcher (what the British would call a “shunter”)
0-8-0 Eight-wheel switcher
2-4-2 Columbia
2-6-0 Mogul
2-6-2 Prairie
2-8-0 Consolidation
2-8-2 Mikado
2-8-4 Berkshire
2-10-0 Decapod
2-10-2 Santa Fe
2-10-4 Texas
4-4-0 American
4-4-2 Atlantic
4-6-0 Ten Wheeler
4-6-2 Pacific
4-6-4 Hudson
4-8-0 Twelve Wheeler
4-8-2 Mountain
4-8-4 Northern
4-12-2 Union Pacific

Some names were fairly unimaginative but easy to remember – six-wheeler, eight-wheeler, ten wheeler and twelve wheeler (I like “Decapod”, meaning ten-legged, for the 2-10-0). Some originate in the names of the railroad companies that ordered the first batches, while others had names that really were the result of someone’s imaginative thinking. When it came to types named after railroads, the same locomotive could have various names depending on how much the purchasing railroad wanted to be identified with the locomotives they’d just acquired, or how much they objected to using the name given by a competitor!

The 4-8-4 “Northern” type is a good example – other roads gave it names that they considered (usually rightly) more fitting: “Dixie” (NC&StL), “Golden State” (SP), “Greenbriar” (C&O), “Niagara” (NYC), “Pocono” (DL&W), “Potomac” (Western Maryland), and “Wyoming” (LeHigh Valley).

SP&S E-1 Class Northern

One of the earliest of these types is the 4-4-0. It has been around since the 19th century (patented by Henry Campbell in 1936) and is famous for many reasons, not least for its part in Buster Keaton’s movie “The General” (recreating the “great railroad chase” that happened during the American Civil War). At the time, it was such a big improvement on previous designs, that it was quickly adopted and became known as the American Standard type, or simply “American” for short. Interestingly, this configuration was exported to Britain, from where the original steam locomotives acquired for US railroads had been purchased, showing that the USA no longer relied on importing technology from the “old country”.

When trains got heavier and more power was needed, locomotives got bigger. Although it was still around even after WW2, the trusty 4-4-0 evolved into the 4-6-0 with an additional driving axle, and probably for that reason, and to distinguish it from the “American”, it was named “Ten Wheeler”.

The “Ten Wheeler” suffered because the designers hadn’t quite worked out how to get a pilot truck (leading bogie) with two axles to do its job properly – piloting (guiding) the driving wheels into curves. It was soon overshadowed by designs that had simpler, single-axle pilot trucks. These were the 2-6-0 Mogul and 2-8-0 Consolidation. Where did those strange names come from?

There’s disagreement over the origin of “Mogul”. My vote goes to the idea that it came from a locomotive named “Mogul” that was built in Britain, by Taunton Locomotive Manufacturing Company in 1866, for the Central Railroad of New Jersey.

It’s not clear whether the 2-8-0 was a progression of the 2-6-0 or the 0-8-0. In any case, the name “Consolidation” was bestowed on the first 2-8-0 built by Matthias Baldwin in 1866, ” in honour of the recent consolidation of the Beaver Meadow, Penn Haven & White Haven and Lehigh & Mahanoy railroads into the Lehigh Valley. After that, all 2-8-0 locomotives would be referred to as “Consolidations”.

AT&N Consolidation Class 280-157

By the early part of the 20th century, it was becoming understood that a factor limiting the power of locomotives was their ability to generate enough steam to satisfy the demand from the cylinders. Designers began to appreciate the importance of the size of the firebox and in particular the area of the grate, besides the overall size of the boiler. To accommodate a wider grate, they began to put the firebox above a trailing truck instead of sandwiched between the rear driving wheels. The 2-6-2 was an early example. In the USA, the first 2-6-2 tender locomotives were built, in 1900, for the Chicago, Burlington and Quincy Railroad, for use on the Midwestern prairies, and so the name “Prairie” was given to this type. That name was another export from the USA to Britain.

There was a kind of hiccup in locomotive design with the introduction of wheel configurations featuring trailing wheels that, instead of being in a pivoting truck, were attached to the rigid frame. These didn’t help to improve the design of the fireboxes. The types, both built by Baldwin, were the 2-4-2 “Columbia” – so-named because it was built (in 1893) for the World’s Columbian Exhibition (in Chicago) – and 4-4-2 “Atlantic”, as the first batch were purchased by the Atlantic Coast Line railroad.

Continuing on with the improvements that could be gained from mounting the firebox (and cab) above a trailing truck, along came the first of the so-called “second generation” configurations, the 4-6-2. At the beginning of the 20th century, two railroads began to receive their 4-6-2 locomotives at about the same time – the Missouri Pacific (from Brooks Works) and the Chesapeake & Ohio (from Alco). The name “Pacific” stuck – perhaps because it was easier to say, or just more catchy? It certainly caught on and became synonymous with high-speed passenger services, and again, not only in North America.

Southern Pacific GS-4 Add-On

The next of the second generation locomotive types was the 2-10-2, stretching the earlier 2-10-0 by adding a trailing truck and gaining more horsepower. The first examples went to the Santa Fe, and hence the name.

Now we come to one of my favourites – the third of the second generation types was the 2-8-2 “Mikado”. How did a North American steam locomotive wind up with a Japanese-sounding name? Baldwin shipped some 2-8-2 locos to Japan in 1906, and thanks to the Gilbert and Sullivan comic opera of the same name, set in Japan, the type picked up the name “Mikado”. However, for reasons that are surely obvious, some railroads changed the name during WW2 to “MacArthur” (but it didn’t stick, and afterwards even UP and the others went back to calling them Mikados).

The fourth and final second-generation type was the 4-8-2 “Mountain”. There are contending stories as to how the name came about. They were initially destined to haul heavy freight trains on the mountainous central section of the North Island Main Trunk Railway, but they were also used by the Chesapeake and Ohio Railway to haul heavy passenger trains between Charlottesville and Clifton Forge, and the C&O named the type after the Allegheny Mountains.

The 2-8-4 was the brainchild of Lima’s engineering team led by the brilliant William E. Woodard (considered by many to be the father of the steam “superpower” era, or “third generation”). There was one railroad company in particular that was at the forefront of encouraging and adopting new technology – the New York Central. The first of Lima’s 2-8-4 locomotives, classed A1, was lettered for the NYC’s Boston and Albany railroad, operating a line over the Berkshire Mountains of western New England. The A1, which was astoundingly successful in trials, was going to be called the “Lima” type, but as it turned out, it was named “Berkshire” after the mountains where it had proved its worth.

NKP S-2 Class Berkshire

In the USA at least, the 4-6-2 Pacifics were eventually found to be lacking. On the NYC, in the mid 1920s, even more power was needed to haul the heavier all-steel cars of their premier trains. They set about applying the new techniques of the super-power era and came up with the 4-6-4. Six drivers would be enough to provide the speed while keeping down both the weight and cost, while the 4-wheel trailing truck was essential for supporting the large firebox and grate. Fittingly for the NYC, the 4-6-4 became the “Hudson” (although Milwaukee Road insisted on “Baltic”).

There are many more stories about particular names, but to round off this topic, let’s not forget the articulated types. Here are a few of the more famous names:

2-8-8-4 “Yellowstone” – the first of this type, called the Z5 class, were among the first of the articulateds built by Alco for Northern Pacific, at the start of the “super-power” era, in 1928.

4-6-6-4 “Challenger” – designed originally for UP’s Sherman Hill – Wahsatch region. The name came from a comment about the proposed initial test run – “that is a challenge for any locomotive!”.


4-8-8-4 “Big Boy” – considered by many to be at the pinnacle of American steam locomotive design, this type was another brainchild of Union Pacific, and it could have ended up being called “Wasatch” or “Sherman”, but somehow the name chalked on the smokebox door by a workman in the Schenectady erecting bay stuck, and we have the lovely “Big Boy” instead.

Union Pacific Big Boy

I’m sure to have left out someone’s favourite, but hopefully this has given you all a feeling for the rich and colourful history of the North American railroads, which is reflected in those wonderful names.



  • The 4-6-2 PACIFIC class had it’s origins in the 3′ 6″ gauge Q CLASS 4-6-2 built for the New Zealand Government railways in 1901. The Q class was designed to burn soft, low calorific value South Otago Lignite, and required a wide firebox. Baldwin originally proposed a 4-6-0 CAMEL BACK, Chief Mechanical Engineer Beattie did not like that idea and proposed a 4-6-2 wheel arrangement. The Q class were a huge success. Baldwin workers referred to them as “those Pacific engines” and the name stuck, Baldwin introduced them as a standard line The worked until 1957 when the last of the class was withdrawn from the West Coast (South Island) branch, sadly, none were preserved:

  • Mike, like your locomotives, this article is well thought out and pretty detailed while remaining user friendly. Thanks for the article and all the fantastic work you’ve done to enhance the train simulator experience!

  • Very nice, informative and eye-opening article! It’s a pity that after moving it to train-simulator.com pictures have gone:(

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