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.

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.

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 coupling wheel diameter of 68 inches, which became class D7 from 1895, and 61 with a coupling wheel 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 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.

To overcome the disadvantages of the class E1 Camelback Atlantics, the E2 was developed in a conventional arrangement. The elimination of the Wootten firebox reduced the grate area from 69 to 51 square feet and eliminated the combustion chamber, but increased the heating area from 2,320 to 2,430 square feet. The dimensions of the cylinders and wheels remained the same, and the same three-axle tender was used. Only the later variants received four-axle tenders.

After 82 of the class E2 built at Altoona, a total of 93 of the class E2a were built from 1902. They differed from the original model mainly in the Belpaire firebox and 32 of them came from ALCO-Schenectady. In 1903 and 1904, 70 E2b were built, which still had Stephenson valve gear, but now had piston instead of slide valves. Four of them formed the basis for the E28 and E29 class compound locomotives. Parallel to the E2b, 22 E2c were built, which again had slide valves. Finally, between 1906 and 1908, 32 E2d followed, which now had Walschaert valve gear and piston valves. In order to achieve a higher adhesive weight, the three carrying axles were loaded by a total of around five tons less than on the E2c.

A large number of locomotives of the various E2 variants were later superheated. This included the E2sd class, which compared to the E2d showed hardly any differences apart from the superheater. Others were rebuilt to different variants of the E3 and E7. These had larger cylinders and some smaller coupled wheels.

The E3 was an Atlantic that was built by the PRR parallel to its E2 that was largely similar, but had larger cylinders. Between 1901 and 1910, a total of eight E3, 114 E3a and 56 E3d were built in the Juniata shops at Altoona. With 80 inch drivers they could not produce a high tractive effort, but with the introduction of steel passenger cars this was offset by operating them double-headed.

After the more powerful E6 Atlantics had been introduced, the E2 and E3 were called “Light Atlantics”. Beginning in 1912 they were superheated and their boiler pressure was reduced from 205 to 195 psi. In this process, a total of 90 E2a, E2d, E3a and E3d became the E3sd. They were used until the thirties and all were scrapped.

For local service, the PRR needed a locomotive with great tractive effort and fast acceleration, as there were many grades. In order to be able to prevent double heading with locomotives with two driving axles, a locomotive with three driving axles was required. The choice fell on a ten-wheeler, i.e. on the wheel arrangement 4-6-0. The boiler could be taken from the class E-6s Atlantic and the class H-10s Consolidation. 

The mass balancing was designed as good as possible and moving parts were constructed as light as possible without sacrificing strength. Despite a wheel diameter of only 68 inches, a top speed of 70 mph could be approved.

The Altoona workshops made 90 locomotives for the PRR and 31 identical ones for the Long Island Railroad. The locomotives apparently fulfilled their purpose, since they achieved the required acceleration performance and could easily keep to the timetables. Despite this, it was reported that they had insufficient running smoothness and a high consumption of coal and water. However, they remained in service as long as there was steam service on the PRR.