The Denver & Rio Grande had the Class 60N built by Grant and Baldwin as standard freight locomotives starting in 1877. These were Consolidations, which were tiny compared to later locomotives on the three-foot gauge. Baldwin's machines had a larger boiler than Grant's. They later received the class designation C-16 from the Denver & Rio Grande Western. Some later received slightly larger wheels and higher boiler pressure. After the new Mikados took over the majority of traffic, the Class 60N was significantly decimated in the 1930s. It could only remain in use where no other locomotives could be used due to the axle load. Today Grant's number 223 remains, having been under restoration for years.

After the Consolidations of the classes 56 and 60, the D&RG received twelve larger class 70 locomotives in 1881. They were used, among other things, as helpers on a four percent steep incline. Five locomotives were converted to standard gauge in the late 1890s and later reverted to three feet. When the D&RGW was reorganized they became the Class C-19 because they now had a starting pull of about 19,000 pounds thanks to new boilers rated at 160 psi. The number 400 still exists today and has been in service for more than 140 years.

The K-27 class was the last compound locomotive built for D&RGW. The “K” stood for “Mikado” and the number for starting tractive effort of 27,000 pounds. Its engine had four cylinders and was of the Vauclain type, but was replaced by a simple two-cylinder engine just four years after delivery. As with other narrow-gauge locomotives of the D&RGW, the axles were in an outside frame. The nickname “Mudhen” came about because with the original engine they often derailed. Most K-27s were scrapped in the fifties and the last two built still exist today. No. 463 runs on the Cumbres & Toltec Scenic Railroad and No. 464 is owned by the Huckleberry Railroad and last ran in 2019.

When 20 years had passed since the later class K-27 was purchased from Baldwin, the D&RG purchased ten additional locomotives from ALCO-Schenectady. These were also Mikados with an outside frame, in which the cylinders, driving and coupling rods, as well as the valve gear were located on the outside. They were initially listed as class 140 and were renamed into the now better-known class K-28 after the D&RGW was founded.

They were the first D&RG locomotives to have a superheater from the beginning. The fact that the class designation indicates only a slightly higher tractive power compared to the K-27 is due to the fact that the drivers now measured 44 instead of 40 inches. However, this, combined with better mass balancing, ensured higher speeds, which is why the crews nicknamed them the “Sports Models”.

During World War II, seven were drafted by the military and taken to Alaska, where they served on the White Pass & Yukon. These were scrapped after the war, while the other three remained in use with the D&RGW until the fifties. They then came to the Durango & Silverton, where they have been pulling tourist trains ever since. The 473 is still in use today, having been converted to oil firing in 2022.

As the penultimate series of steam locomotives for the three-foot gauge, the D&RGW procured the K-36 from Baldwin, ten of which were delivered in 1925. The “K” in the designation stood for the Mikado design, the number for the tractive force in thousands of pounds. As with its predecessors, the coupling wheels were mounted inside the outer frames and the coupling and connecting rods, valve gear and cylinders were attached outside the frames. The balancing weights were not integrated into the wheels either, but mounted on the outside.

The K-36 was initially used only in front of freight trains. In 1937, three examples were fitted with steam heating and communication lines for use in front of passenger trains. Three more followed in 1945, leading to more than half being equipped accordingly. One locomotive was so badly damaged in an accident on the turntable in 1955 that it could only be used as a spare parts donor. The other nine were removed from active service with D&RGW between 1962 and 1970.

It is unusual for a steam locomotive from the 1920s that all nine engines which were not destroyed in an accident are still preserved and eight of them are still operational. Five of these are now owned by the Cumbres and Toltec Scenic Railroad, four of which are in regular service. The other four are now owned by the Durango and Silverton and are also used regularly. One of each of the two operators was converted to oil firing around 2020.

One of two classes of 4-6-6-4 “Challenger” locomotives ordered by the DRGW was the L-105 introduced in 1938. It was designed for mixed service on grades in the Rocky Mountains with up to three percent and sharp curves. For these long grades, it had a huge sandbox mounted in front of the smoke box. The 105 in the class designation denoted the starting tractive effort in thousands of pounds. 

The first ten were delivered by Baldwin in 1938 and got the numbers 3700 to 3709. In 1942, five more were ordered which got the numbers 3710 to 3714. They had the same basic dimensions, but got fewer tubes and flues. A typical line the L-105 was running on went over Soldier Summit in Utah. There they hauled 2,750 tons and were assisted by helpers on the steepest portions. The town called Helper was one of those places where the helpers were coupled to the train. They were retired and scrapped between 1951 and 1957.

In order to achieve greater pulling power, the D&RGW further developed their Mallets from the L-95 and L-107 classes to the L-131 class with single steam expansion. With the wheel arrangement 2-8-8-2 and an axle load of over 70,000 pounds it was possible to build a boiler with one of the largest fireboxes at that time. The class designation indicates a starting tractive effort of 131,000 pounds, although the commonly used formula gives about 140,000 pounds. However, the D&RGW determined the practically achievable pulling force to be 131,800 pounds and then rounded this value down.

In 1927, the first ten locomotives were built by ALCO-Brooks. Their service area was at the continental divide, where there was a steepest gradient of 1.42 percent on the east side and of 3 percent on the west side. The train tonnages for one of these locomotives were 3,300 short tons on the less steep side and 1,400 short tons on the steeper side. The drivers apparently complained about excessive smoke production, which became a major problem, especially in tunnels.

When ten locomotives of another series were built in 1930, the dimensions of the power plant did not change. To distinguish them, this time the tractive effort was rounded up and it was called L-132. These were now built at Schenectady and received a new boiler design. Much of the tubes were replaced with the larger flues, which contained additional superheater elements. Like the L-131, they remained in service until the mid-1950s, when the conversion to diesel took place.