The “John Bull” was a locomotive built by Robert Stephenson & Co. in England and was among the first to be used in the United States. It was built in 1831, initially as a 0-4-0 and was shipped disassembled to New Jersey. There it was reassembled by the Camden & Amboy and christened “John Bull”, which was a personification of England. Since only horses were used in the construction of the railroad, the locomotive was not used until 1833, after it opened.

It initially had no cab and the tender was a home-made design that used a whiskey barrel as a water tank. After it derailed several times on the cheaper laid American tracks, a leading axle including a cow catcher was added, which gave it its well-known, distinctive appearance. The coupling rods were removed, meaning only the last axle was powered. Later it received a real tender and then a cab.

This nickname was soon officially adopted, so the name “Stevens” fell out of use. Its active service with the Camden & Amboy lasted until 1866. After the PRR purchased the C&A in 1871, it was restored and used for various public demonstrations. It came into the possession of the Smithsonian in 1884 and was not moved for a long time. After the PRR had a working replica built in 1939, the original was moved again under its own power in 1981 for its 150th birthday, making it the oldest operational locomotive in the world.

The “Monster” was an early four-axle locomotive with all wheels driven. The original locomotive was designed by Isaac Dripps and built in 1840 by the Camden & Amboy. The cylinders were situated in an inclined position above the second axle and acted on levers at the front of the locomotive. This power was transmitted to the third axle via connecting rods and the coupling rods only drove the fourth axle. The second axle was driven by the third one through a set of spur gears. Finally, a second set of coupling rods drove the first axle.

It was among the first, if not the first locomotive at all that was designed for burning anthracite. Its firebox had a combustion chamber and a water leg that created additional water circulation. In 1852 and 1853, long after the original locomotive had been built, two more each were built by the Trenton Locomotive Works. Some years later, Dripps rebuilt them to 4-6-0 locomotives. In this form, they were used until around 1875.

In 1851, the Cumberland Valley had a tank locomotive built by Seth Wilmarth, which was intended for passenger trains with a small number of passengers. The basic idea was to keep the ratio of the empty weight of the locomotive to the weight of the train as advantageous as possible in order to save costs. It had the wheel arrangement 2-2-2, which was generally very rare in tank locomotives and was hardly found in the USA, even with tender locomotives. In addition to the “Pioneer” there was also the almost identical “Jenny Lind” and two other very similar locomotives.

The “Pioneer” could accelerate a train of four passenger cars to 40 mph and achieved a high mileage for several years for its standards. After the Civil War, it was used to haul work trains because its power was no longer sufficient for modern passenger trains. Although it was later put into storage, it officially remained in service until 1901. It was then donated to the Smithsonian Institution and used as a working display at appropriate events.

The PRR had lots of tracks on streets and on industrial property with tight curves, where even locomotives with three sets of drivers had problems. So they were probably the last US railroad to design a huge standard gauge switcher with the wheel arrangement 0-4-0 in 1916. After the older class A4, the new A5s was superheated and 7,000 pounds heavier. It had Walschaerts valve gear, piston valves and larger cylinders at 20 by 24 inches. The firebox was of the Belpaire type typical for the PRR and its grate was larger than that of the USRA 0-6-0 at 38.33 square feet. By 1924, the Juniata works at Altoona had completed 47 locomotives. They started to be replaced by diesel switchers in the late forties. The last one was retired in 1957 and 94 is the only one that was preserved. Today one can find it in the Railroad Museum of Pennsylvania in Strasburg.

In order to be able to burn anthracite coal efficiently, class AAn was developed from class K (later D6). The K already had a wide firebox above the drivers, which was optimized here for the use of anthracite. There were 58 locomotives with a driver diameter of 68 inches, which became class D7 from 1895, and 61 with a driver diameter of 62 inches, which became class D7a.

When it came to switchers, here called “shifters”, the PRR stuck to locomotives with a maximum of three axles, but still sufficient tractive power until the mid-20s. The most successful class here was the B6, of which a total of 372 were built between 1902 and 1920. It started with 79 of the basic B6, which were operated with saturated steam and had the Belpaire firebox typical of the PRR.

From 1913 onwards, 55 B6sa followed, which had a round firebox and were factory-built with a superheater. The largest number was reached by the B6sb with 238, which again had a Belpaire firebox. The B6 were also later rebuilt with superheaters and referred to as B6s. Today there are still two B6sa and B6sb, both of which are not operational.

The Pennsylvania Railroad's class C1 was the heaviest 0-8-0 locomotive ever built. It had a service weight of 278,000 pounds and a maximum axle load of 74,000 pounds on the first axle. Due to its long wheelbase of 15 ft 9 in, however, the tracks were damaged and there were also frequent derailments. As far as possible, only switching locomotives with a 0-6-0 wheel arrangement were used. Nevertheless, the C1 was able to demonstrate its high tractive power on hump yards. The 90 locomotives were retired between 1948 and 1953.

In 1919, Baldwin built ten large 0-8-8-0 Mallets for the PRR. They were designated CC2s and like the CC1s prototype of 1912, they were intended as switchers on the hump yard, as pushers and for transfer services. There they had to run over grades of five percent and through tight curves. By designing the locomotive without leading or trailing axles, all the weight was used for adhesion. Curve negotiation was guaranteed by tight spacing of the relatively small wheels on each group.

Compared to the CC1s, the CC2s had a larger boiler, larger cylinders and smaller drivers with a diameter of only 51 inches. In the result, the starting tractive effort was nearly 100,000 pounds. In contrast to most PRR locomotives, they had no Belpaire firebox. Anyway, their fireboxes had a combustion chamber and arch tubes. They were scrapped between 1947 and 1949.

In principle, the PRR class D can be described as the first Moguls, but the leading axle was fixed in the frame. The driving axles with small wheel diameters were well spaced within the frame. The tender already had four axles, but only the first two were in a movable bogie and the rear ones were fixed in the frame.

Although the locomotives were generally described as being a good design, the smooth running was apparently not entirely convincing. This is the way to explain why the chassis was later rebuilt. Some locomotives were rebuilt to 4-4-0 with larger wheels. A third driving axle was installed later again, resulting in a 4-6-0 wheel arrangement. They were scrapped in the late 1860s.

The Pennsylvania Railroad wanted to accommodate a larger grate area in Atlantic locomotives in order to be able to burn anthracite and fragments thereof. For this purpose, three locomotives were procured on a trial basis, which had a combination of Wootten and Belpaire fireboxes and were designed as Camelbacks. The special shape of the firebox and the combustion chamber resulted in 218 square feet of direct heating surface and a grate surface of nearly 70 square feet. A visual highlight was the common cover of the steam dome and the sandpit, which looked like a huge steam dome. 

The approximately 410-ton express trains between Philadelphia and Atlantic City could be transported over longer sections at an average speed of around 55 mph. With only 260 tons on the hook, an average speed of 70 mph was achieved on the 58 miles long, slightly descending section from Camden to Atlantic City.

Ultimately, however, the PRR was bothered by the fact that the engine driver and the fireman had difficulty communicating. Hundreds of other Atlantics were procured as a result, but all of them with a conventional firebox and cab at the rear end. The three engines were sold to the Long Island Railroad in 1901 and scrapped in 1911.