The class R-1 Mountains were the last steam locomotives ordered by the Boston & Maine. They were among the heaviest Mountains and were built in four batches between 1935 and 1941. Initially five R-1a were built, in 1937 another five R-1b, in 1939 three R-1c and finally five R-1d. All locomotives were given names that were determined in a competition.

From the R-1b onwards, the spoke wheels on the driven axle were replaced with disc wheels. The R-1c was almost identical to the R-1b, only the R-1d underwent major changes. It now had disc wheels on all drivers and the Coffin feed water heater was replaced with a Worthington one. In addition, there was now a seven-axle tender instead of the six-axle one. Thirteen R-1s were sold to the B&O in 1947, the remaining five were scrapped in 1955 and 1956.

U-1c No. 6039 in August 2006 in Steamtown, Scranton, Pennsylvania

US National Park Service

The Grand Trunk Western received five U-1cs from Baldwin in 1925, which were similar to parent company Canadian National's U-1a and b. They were modern Mountain type locomotives that were suitable for passenger, express and freight trains. They had a feed water heater and a stoker and were the first GTW locomotives with a Vanderbilt tender. Beginning in 1929, the CLC delivered five U-1d and the Montreal Locomotive Works twelve U-1e. The sub-variants d and e are largely the same, but differ in the Walschaert and Baker type valve gear.

When hauling the new steel passenger cars over the Allegheny Mountains, the class F-15 Pacific locomotives quickly reached their limits, so that the trains could not consist of more than six cars. As a remedy, a new type of locomotive was designed in which, compared to the Pacific, a fourth coupled axle was added and the diameter of the wheels was slightly reduced in order to obtain more adhesive weight and to be able to install a larger boiler. Since this was the first locomotive with a 4-8-2 wheel arrangement in North America, the C&O gave the design the name “Mountain”.

Compared to the F-15, the tractive effort was almost doubled and the indicated power increased to almost 2,500 hp. Ten steel cars with a total weight of around 600 tons could now be hauled over the Alleghenies without any problems. With this load, you could reach 25 mph at 2.52 percent, and even 70 mph were reached on the flat. However, a disadvantage of the smaller coupling wheels and the special design of the Heusinger valve gear was that the engines exerted a very high hammer blow on the rails. As a result, only three class J-1 locomotives remained and from then on significantly more powerful Pacific class F-16 and F-17 locomotives were procured for the same task.

During World War I, the J-1 had to haul heavy freight trains across the Alleghenies. After the end of the war, seven examples of the USRA Heavy Mountain were procured and designated Class J-2. These put less strain on the rails with larger coupling wheels and Baker valve gear and, due to the increased boiler output, were able to generate approximately the same tractive effort.

In the 1920s, the J-1's valve gear was optimized with the help of new knowledge in order to reduce the known problems. In addition, the J-2s were soon fitted with Heusinger valve gear and were then referred to as the J-2a. In the 1930s and 1940s they were overtaken by the new J-3 and L-2 class locomotives, which initially led to the J-1 being phased out by 1948. Shortly thereafter, the C&O passenger trains were converted to diesel traction, which also meant that the J-2 was retired by 1952.

With the development of mining in North Korea, freight locomotives were needed that could be used on the winding mountain routes. The 2-8-2 type was already used for heavy freight trains, but there were concerns about excessive wear on wheel sets and rails due to the many tight curves. Thus, a leading bogie was used and the engines were called "Matei", which came from the American name "Mountain".

Development took place in Gyeongseong along with the Pacific Pashiko class locomotives, and that's where the first two examples were built. For the other 48 locomotives, the production order was given to Kisha Seizo in Japan. The locomotives had a modern look with large smoke deflectors and a common cover for the dome and the feedwater heater. The grate of 67 square feet was fed by a mechanical stoker.

During World War II, six examples were either destroyed or stolen by the Soviet Army. After the division of Korea, some of the rest came to the northern and southern parts of the country. In South Korea they became the Mateo1, while in the North they were referred to as the Madoha class. In the north they were also used in front of passenger trains and their long service life can be seen from the fact that they were re-classified as the 7100 series in the 1970s.

Even before the 07 1001, the Reichsbahn had rebuilt another French steam locomotive for firing with coal dust and numbered it 08 1001. It was a member of the class 241 A, which was built in 1931 for the French Eastern Railway and rested in Greifswald non-operational until 1952. As one of the few Mountain steam locomotives in Europe with a 4-8-2 wheel arrangement, it was an extraordinarily powerful express locomotive and was therefore ideal for trials with coal dust. 

Like the 07 1001, it had a four-cylinder de Glehn compound engine, the low and high pressure cylinders of which acted on the first and second driving axles and could be controlled separately, which was rarely used in Germany. The large combustion chamber favored the new type of firing, and so the rebuilding process began in 1952. However, the locomotive could not prove its efficiency because the boiler pressure had been reduced from 20 to 16 bars and the maximum speed was set at 110 km/h for safety reasons. The result was that the expectations had not been met and the locomotive was scrapped after just 34,000 km. The tests were then continued with the 07 1001, but also with relatively little success.

The last steam locomotives that the Florida East Coast purchased new were 23 copies of the USRA Heavy Mountain. They were delivered by ALCO-Schenectady in 1926 and were numbered 801 to 823. After the Mountains of the classes 301 and 401, they were significantly heavier. In direct comparison with the 401, they had a larger boiler and larger cylinders, but smaller drivers for greater pulling power. After three were lost by 1952 due to boiler explosion or accident, the remaining 20 were scrapped in 1954.

Although the electrification of the French main lines was already foreseeable shortly after the end of the Second World War, particularly powerful steam locomotives were needed for the transitional period. Since express trains with up to 20 four-axle coaches had to be hauled on mountainous main routes, an output of around 4,000 hp was required. The choice fell on a locomotive with a 4-8-2 wheel arrangement, which was also called the “extended Pacific” in France. The 241 P developed in this way was the last steam locomotive in Europe with this wheel arrangement.

The 241 C of the PLM from the year 1930, which had only been built once, was used as the basis. In the De Glehn four-cylinder compound powerplant, the high-pressure cylinders were located within the frame between the first and second coupled axle and drove the third coupled axle. The low-pressure cylinders were level with the middle of the bogie and drove the second coupled axle. André Chapelon was involved in optimizing the steam paths in the boiler and powerplant, but did not have the opportunity to redesign the design in depth. In addition, a double, cloverleaf-shaped blowpipe based on the PLM design and a mechanical stoker were installed.

241 P 1 on a post card of 1950

Compared to the 241 C, the 241 P achieved about 20 percent more power. While the predecessor did not make it into series production, a total of 35 examples of the 241 P were built up to 1952. As standard they received a tender with 34 cubic meters of water and twelve tonnes of coal, but alternatively tenders with 36 cubic meters of water and only nine tonnes of coal were also used.

The engines first came to the Sud-Est and Nord regions. After the most important main lines there were electrified, some were moved to other lines within the regions and others were moved to the Est and Ouest regions. In the 1960s, they were able to prove their power one last time when they had to stand in alone to replace broken A1AA1A 68000 diesel locomotives, which were otherwise used double-headed.

In January 1969, 17 of the 35 pieces were still in use. In that year, the number of remaining engines decreased rapidly, so that the last regular operations took place on September 28, 1969. Four engines have been preserved, with number 17 being the only operational one to date, making it the most powerful operational steam engine in Europe. Number 9 could also become operational again in the future.

The Great Northern was one of the first railroads in the United States to order Mountain locomotives. The manufacturer Lima saw these as Mikados, which had a two-axle forward bogie for better running characteristics in passenger service. The Great Northern wanted to use the P-1 to eliminate the need for helpers on passenger trains in Montana and the Cascades.

They had a conical boiler with a Belpaire firebox. The first ten P-1s were coal-fired and the last five were oil-fired. The diameter of the drivers was only 62 inches or 1,575 mm, which was an advantage on the steep lines. The speed of passenger trains was now 20 mph (32 km/h) on the 1.8 percent in Montana and 15 mph (24 km/h) on the 2.2 percent in the Cascades, both without helpers.

When these locomotives were no longer sufficient to meet the increased requirements, in 1928 all P-1s were rebuilt into 2-10-2 freight locomotives and designated class Q-2. The drivers and the cylinder diameter were each increased by one inch. The boiler only remained the same on the outside and had many changes on the inside, as well as a higher pressure. They were all coal-fired, but nine were converted to oil in the 1940s. Their decommissioning began in the 1950s and was completed in April 1958.