"Mikado" is the name generally assigned to the steam locomotives of the 2-8-2 wheel arrangement. The general, and reasonable assumption, is that this appellation stems from the construction of locomotives of this wheel arrangement by Baldwin in 1893. These locomotives were of the three foot six inch gauge, and were constructed for Nihon Tetsudo (Japan Railways), a private railway at the time. The class of these first locomotives was "Bt4/6". "B" was for "Baldwin", "t" meant "with tender", "4" stood for drivers, and "6" was for total axles. In 1906, 17 private railways, including Nihon Tetsudo became part of the Imperial Japanese Government Railways. It should be pointed out that after Pearl Harbor, in an excess of patriotic zeal, some railroads (most prominently the B&O and Union Pacific) renamed their locomotives of this wheel arrangement as "MacArthurs".

The first known example of this wheel arrangement in North America was on the Lehigh Valley. In 1883, that road rebuilt one of two center cab 2-10-0s into a 2-8-2. The thought here was to reduce flange wear on the final set of drivers. The Lehigh Valley was one of the early pioneers of the 2-8-2, purchasing no less than 47 center cab Wooten firebox equipped locomotives between 1902 and 1905. While other anthracite roads, and the Lehigh Valley itself, were to purchase further Wooten equipped Mikados, this group was the only class to fall into the category of "Camelback - Mother Hubbard".

Early installations of locomotives of the 2-8-2 wheel arrangement, both narrow gauge and industrial, such as logging, were ordered with a trailing axle to permit ease in bi-directional operation. But, for road service, the Mikado was considered to be developed from the 2-8-0 and the 2-6-2, just as the Pacific was a product of both the 4-4-2 and the 4-6-0. Bruce ("The Steam Locomotive In America") gives credit to an Alco built class for the Northern Pacific of 1905, which had 63 inch drivers. This, he regards as a development of 2-6-2s, of which the NP had a considerable fleet. The additional axle and the larger boiler permitted by the longer wheel base resulting in the 2-8-2 having the potential to haul the same trains as the 2-6-2 but on heavier grades. Another authority (Robert LeMassena, ("America's Workhorse Locomotive, the 2-8-2") points out that the NP sort of 2-8-2 had a smaller grate than contemporary 2-8-0s with 63 inch drivers, and the first true example of the 2-8-2 was a class built for the Virginian Railway in 1909, which had a deep firebox, supported by the trailing truck and a large superheated boiler.

Whatever the ancestry, the 2-8-2 became the principal freight locomotive of North America. Dealing only with standard gauge locomotives of common carrier railroads, Bruce gives a total of 9500 having been built for service in the United States. To this should be added 497 of the type on the roster of the Canadian National, and 253 for the Canadian Pacific, plus an uncertain number for smaller Canadian roads. Although the Nacionales de Mexico ultimately purchased many 2-8-2s from US railroads. One record shows an order for 40 57-inch driver locomotives in 1921/23. The North American total, then, as of about 1945, when pretty much all built would still have been in service, is somewhere in excess of 10,000 locomotives. Reasonably, then, about one out of every five locomotives in service on North American common carrier railroads was a Mikado (or MacArthur).

What were the characteristics that made this class so popular and successful? It was relatively a large locomotive - few were built with axle loadings of less than 50,000 lbs, and at least half were at 60,000 lbs and above, which resulted, at normal adhesion, in starting tractive efforts substantially over 50,000 lbs. In other words, when dealing with general purpose freight service, the ability to handle trains of 3000 to 5000 tons at good track speeds was accomplished with Mikados. It was a beautifully balanced design with the lead axle and the two front driving axles being equalized with the two rear driving axles and the trailing axles. Grate areas were in the general area of 65 to 70 square feet, although there were larger ones, including some giants on the Great Northern with an incredible 98.5 square foot grate. Railroads which desired to burn anthracite equipped their Mikados with Wooten fireboxes, which were large but shallow. Although some early examples were built as saturated engines, and some were compounds, it is safe to assume that all of the 10,000 Mikados were superheated and simple by 1945. Such appliances as boosters and feedwater heaters, if not original equipment, were frequently retrofitted, and with the obvious exception of oil burners, it is safe to say that almost all Mikados fell within the ICC parameters for stokers being required.

Some coal haulers, the Virginian for one, stayed with 56/57 inch drivers for their Mikados. For the most part, however, driver diameters fell between a range of 61.5 inches (Reading) and 64 inches (B&O, Burlington). These diameters are really a matter of the preference of the various roads, thus, the Pennsylvania and the B&O both preferred even numbered diameters, but the PRR rounded down to 62 inches and the B&O, up to 64. The Reading went into the Twentieth Century with 55.5 inches as a standard wheel diameter for freight locomotives. When they ordered their first 27 Mikados in 1913, as fast freight engines, they got daring and fitted them with 61.5 inch drivers. Then, timidity took over, and the 1917 order for an additional 30 reverted to the 55.5 inch coal hauling diameter. Subsequently, they took a deep breath and installed 61.5 inch diameter drivers on the newer Mikados. With drivers in these diameters, and reasonably sized cylinders and big boilers, the Mikado was easily capable of 50mph and higher speeds. Mikados were built as freight engines, with one exception. The Union Pacific, whose first 2-8-2s had 57 inch drivers, received a second order with 63 inch drivers which were intended for mountain passenger service. One odd feature of these "passenger" engines was this; they were equipped with "Vanderbilt" type tenders, common on the UP at that period, and had a dummy vestibule fitted to the rear of the cylindrical water space. This was to line up with the vestibule of the first car attached behind the tender, and was conceived of as a method of reducing sway, to what effect remains obscure. When the larger Pacifics, and Mountains, were assigned to passenger service on the UP, these Mikados had the vestibules removed and went into freight work. But, Mikados did work passenger trains, particularly on heavy grades and, for example on the B&O and the Pennsylvania, were frequently used as passenger helpers.

Obviously, the type was in widespread use, to the extent that Mikados were the main freight locomotive of the North American railroads. Of course, there were exceptions. Lines which never owned 2-8-2s, included the Boston & Maine, the Delaware and Hudson, the Norfolk & Western, and others. One interesting exception to the domination of Mikados was the Southern Pacific. That system owned 162 Mikados and an impressive 182 2-10-2s (called "decapods" on the SP, for obvious reasons.)