Locomotive classification on the Pennsylvania Railroad took several forms. Early on, steam locomotives were given single-letter classes. As the 26 letters were quickly assigned, that scheme was abandoned for a more complex system. This was used for all of the PRR's steam locomotives, and — with the exception of the final type bought — all electric locomotives also used this scheme.
The M1 was a class of steam locomotive of the Pennsylvania Railroad (PRR). It was a class of heavy mixed-traffic locomotives of the 4-8-2 "Mountain" arrangement, which uses four pairs of driving wheels with a four-wheel guiding truck in front for stability at speed and a two-wheel trailing truck to support the large firebox needed for sustained power. Although built for both passenger and freight work, they spent most of their service lives hauling heavy high-speed freight trains. Many PRR men counted the M1 class locomotives as the best steam locomotives the railroad ever owned.
The Pennsylvania Railroad's class H8, H9s and H10s steam locomotives were of the 2-8-0 "Consolidation" type, the last three classes of such built by the railroad. The three classes differed only in cylinder diameter and thus tractive effort, each subsequent class increasing that measurement by an inch. The first H8 was built in 1907 and the last H10 in 1916; within a few years they were replaced on heavy freight assignments by 2-8-2s and 2-10-0. They became the railroad's standard light freight locomotive, replacing all other class H 2-8-0s, and a number remained in service until the end of PRR steam locomotive operation in 1957. 968 class H8 of various subclasses were constructed, along with 274 class H9s and 273 class H10s. A number of H8 locomotives were rebuilt to H9s specification.
The Pennsylvania Railroad's class B6 was its most successful class of switcher, or as the PRR termed them, "shifter". The PRR preferred the 0-6-0 wheel arrangement for larger switchers, whereas on other roads the 0-8-0 gained preference. The PRR used road locomotives, generally 2-8-0s, when larger power was required.
The Pennsylvania-Reading Seashore Lines was a railroad that operated in southern New Jersey in the 20th century. It was created in 1933 as a joint consolidation venture between two competing railroads in the region.
Class D16 on the Pennsylvania Railroad was their final development of the 4-4-0 "American" type of steam locomotive.
A total of 429 of these locomotives were built at the PRR's Juniata Shops, spread across five subclasses; some had 80 in (2,030 mm) diameter driving wheels for service in level territory, while others had 68 in (1,730 mm) drivers for mountainous terrain.
In the pre-1895 scheme, these locomotives were second class L.
The class D15 of the Pennsylvania Railroad comprised a solitary Lindner-system cross compound steam locomotive of 4-4-0 "American" wheel arrangement in the Whyte notation. The sole locomotive was #1515, built in 1892 at the PRR's Altoona Shops, it had very British lines with a full-length footplate, splashers, a six-wheel tender, and large 84 in (2,134 mm) drivers.
Class D14 on the Pennsylvania Railroad was a type of steam locomotive with a 4-4-0 wheel arrangement in the Whyte notation.
They were originally designated class P in the PRR's pre-1895 classification scheme. Twenty-two locomotives were built at the PRR's Altoona Works ; six in 1893 with 78-inch (1,981 mm) driving wheels, and sixteen in 1894 with 80-inch (2,032 mm) drivers, classified D14a.
Later, all sixteen class D14a were rebuilt to class D14b with 68-inch (1,727 mm) drivers for secondary service after they were replaced in top-flight express service, while three of the six class D14 were similarly rebuilt to class D14c.
Class L1s on the Pennsylvania Railroad comprised 574 2-8-2 "Mikado" type steam locomotives constructed between 1914 and 1919 by the railroad's own Juniata Shops as well as the Baldwin Locomotive Works (205) and the Lima Locomotive Works (25).
It was the largest class of 2-8-2 locomotives anywhere, although other railroads had more Mikados in total.
Class D7 on the Pennsylvania Railroad was a class of 4-4-0 steam locomotive.
Fifty-eight were built by the PRR's Altoona Works between 1882–1891 with 68 in (1.73 m) drivers, while sixty-one of class D7a were constructed with 62 in (1.57 m) drivers.
The Pennsylvania Railroad's steam locomotive class D1 comprised thirteen 4-4-0 locomotives for express passenger service, constructed at the railroad's own Altoona Works during 1868–1872.
They were the first standardized class of locomotives on the railroad and shared many parts with other standard classes.
The Pennsylvania Railroad's steam locomotive class D2 comprised twenty 4-4-0 locomotives intended for mountain passenger helper service, constructed at the railroad's own Altoona Works during 1869–1880.
They were the second standardized class of locomotives on the railroad and shared many parts with other standard classes.
The Pennsylvania Railroad's steam locomotive class D3 comprised sixty-seven 4-4-0 locomotives intended for general passenger and freight service, constructed at the railroad's own Altoona Works during 1869–1881.
They were the third standardized class of locomotives on the railroad and the most numerous of the early standard types; they shared many parts with other standard classes.
The Pennsylvania Railroad's steam locomotive class D4 comprised thirty-seven anthracite-burning 4-4-0 locomotives intended for general passenger and freight service on the PRR's New Jersey lines, constructed at the railroad's own Altoona Works during 1873–1890.
They shared many parts with other standard classes.
The Pennsylvania Railroad's steam locomotive class D5 comprised eighteen lightweight 4-4-0 locomotives for light duty, maintenance-of-way and branch-line service, constructed at the railroad's own Altoona Works during 1870–1873.
The PRR J1 was a class of 2-10-4 or "Texas" type steam locomotives with 69 in (180 cm) driving wheels built between 1943 and 1944. The J1 had over 95,000 pounds-force (422.6 kN) of tractive effort, plus an additional 15,000 lbf (66.7 kN) if the booster engine was used.
The Manhattan Limited was a passenger train of the Pennsylvania Railroad which served the Chicago—New York City route.
The Pennsylvania Railroad's class H6, H6a, and H6b steam locomotives were of the 2-8-0 "Consolidation" freight type, the most numerous class on the railroad with 2,032 units, and the second most prolific 2-8-0 class in North America, with the USATC S160 class rostering 88 units more. The three subclasses differed as follows:
The Pennsylvania Railroad (PRR) class CC2s consisted of an experimental 0-8-8-0 single type of steam locomotive built by Baldwin Locomotive Works in 1919 for PRR; 10 were produced. These were used for transfer runs, and used for switching as "yard hump" power.
