The Pennsylvania Railroad, legal name The Pennsylvania Railroad Company, also known as the "Pennsy", was an American Class I railroad that was established in 1846 and headquartered in Philadelphia. It was named for the commonwealth in which it was established. At its peak in 1882, the Pennsylvania Railroad was the largest railroad, the largest transportation enterprise, and the largest corporation in the world.
The Pennsylvania Railroad (PRR) K4 4-6-2 "Pacific" was its premier passenger-hauling steam locomotive from 1914 through the end of steam on the PRR in 1957.
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 (PRR) class T1 duplex-drive 4-4-4-4 steam locomotives, introduced in 1942 with two prototypes and later in 1945-1946 with 50 production examples, were the last steam locomotives built for the PRR and arguably its most controversial. They were ambitious, technologically sophisticated, powerful, fast and distinctively streamlined by Raymond Loewy. However, they were also prone to wheelslip both when starting and at speed, in addition to being complicated to maintain and expensive to run. The PRR decided in 1948 to place diesel locomotives on all express passenger trains, leaving unanswered questions as to whether the T1's flaws were solvable, especially taking into account that the two prototypes did not have the problems inherent to the production units.
A 4-4-4-4 steam locomotive, in the Whyte notation for describing locomotive wheel arrangements, has a four-wheel leading truck, two sets of four driving wheels, and a four-wheel trailing truck. While it would be possible to make an articulated locomotive of this arrangement, the only 4-4-4-4s ever built were duplex locomotives—with two sets of cylinders driving two sets of driven wheels in one rigid frame, essentially a 4-8-4 with divided drive.
The Pennsylvania Railroad's class B6 was its most successful class of switcher locomotive, or as the PRR termed them "shifter". The PRR preferred the 0-6-0 wheel arrangement for larger switchers, whereas on other railroads the 0-8-0 gained preference. The PRR generally used 2-8-0s when larger power was required.
The Pennsylvania Railroad's S2 class was a steam turbine locomotive designed and built in a collaborative effort by Baldwin Locomotive Works and Westinghouse Electric & Manufacturing Company, as an attempt to prolong the dominance of the steam locomotive by adapting technology that had been widely accepted in the marine industry. One was built, #6200, delivered in September 1944. The S2 was the sole example of the 6-8-6 wheel arrangement in the Whyte notation, with a six-wheel leading truck keeping the locomotive stable at speed, eight powered and coupled driving wheels, and a six-wheel trailing truck supporting the large firebox. The S2 used a direct-drive steam turbine provided by the Westinghouse Electric & Manufacturing Company, geared to the center pair of axles with the outer two axles connected by side rods; the fixed gear ratio was 18.5:1. Such design was to prevent energy loss and S2 achieved a mechanical efficiency of 97% which means only 3% of steam energy was lost within the propulsion equipment. The disadvantage of a direct-drive steam turbine was that the turbine could not operate at optimal speeds over the locomotive's entire speed range. The S2 was the largest, heaviest and fastest direct-drive turbine locomotive design ever built.
The Pennsylvania Railroad's class K5 were experimental 4-6-2 "Pacific" types, built in 1929 to see if a larger Pacific than the standard K4s was worthwhile. Two prototypes were built, #5698 at the PRR's own Altoona Works, and #5699 by the Baldwin Locomotive Works. Although classified identically, the two locomotives differed in many aspects, as detailed below. They were both fitted with a much fatter boiler than the K4s, but dimensionally similar to those of the I1s 2-10-0 "Decapods". Most other dimensions were enlarged over the K4s as well; the exceptions being the 70 square feet (6.5 m2) grate area and the 80 in (2.032 m) drivers.
The PRR S1 class steam locomotive was a single experimental duplex locomotive of the Pennsylvania Railroad. It was designed to demonstrate the advantages of duplex drives espoused by Baldwin Chief Engineer Ralph P. Johnson. It was the longest and heaviest rigid frame reciprocating steam locomotive that was ever built. The streamlined Art Deco styled shell of the locomotive was designed by Raymond Loewy.
The Pennsylvania Railroad's class P5 comprised 92 mixed-traffic electric locomotives constructed 1931–1935 by the PRR, Westinghouse and General Electric. Although the original intention was that they work mainly passenger trains, the success of the GG1 locomotives meant that the P5 class were mostly used on freight. A single survivor, prototype #4700, is at the National Museum of Transportation in St Louis, Missouri.
The Pennsylvania Railroad class Q1, #6130, was a single experimental steam locomotive designed for dual service. The locomotive entered service in 1942, and retired in 1949 after accumulating a relatively low 165,000 service miles.
Pennsylvania Railroad Class L1s were 2-8-2 "Mikado"-type steam locomotives that were used on the Pennsylvania Railroad during the early twentieth century. These 574 locomotives were manufactured 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).
Pennsylvania Railroad 1361 is a 4-6-2 K4 "Pacific" type steam locomotive built in May 1918 by the Pennsylvania Railroad's (PRR) Juniata Shops in Altoona, Pennsylvania. It hauled mainline passenger trains in Pennsylvania and commuter trains in Central New Jersey on the PRR until its retirement from revenue service in 1956. Restored to operating condition for excursion service in 1987, No. 1361 and its only surviving sister locomotive, No. 3750, were designated as the official state steam locomotives by the Pennsylvania General Assembly. In 1988, it was sidelined due to mechanical problems and was currently owned by the Railroaders Memorial Museum (RMM) in Altoona, Pennsylvania, who were currently getting No. 1361 back to operation.
The Pennsylvania Railroad G5 is a class of 4-6-0 steam locomotives built by the PRR's Juniata Shops in the mid-late 1920s. It was designed for passenger trains, particularly on commuter lines, and became a fixture on suburban railroads until the mid-1950s. The G5 was the largest and most powerful 4-6-0 locomotive, except for a single Southern Pacific 4-6-0 that outweighed it by 5,500 lb.
The Pennsylvania Railroad's class E2, E3, E7 steam locomotives were of the 4-4-2 "Atlantic" passenger type, frequently called light Atlantics after the introduction of the heavier E6 Atlantics. All were similar in size and boiler capacity but differed in firebox type, valves and valve gear and cylinder diameter. Classes E2 and E3 were built simultaneously. Starting in 1916 a rebuilding program converted ninety class E2a,b,c to class E7s by replacing slide valves with piston valves and increasing cylinder diameter from 20.5 to 22.5 inches. Fourteen class E2 were similarly converted to class E7sa. Ninety class E2a,d, E3a,d were converted to class E3sd. These improvements allowed many of the engines to remain in active service into the 1930s.
PRR 460, nicknamed the "Lindbergh Engine", is a Pennsylvania Railroad E6s steam locomotive now located in the Railroad Museum of Pennsylvania, outside of Strasburg, Pennsylvania in the United States. It was built in 1914 and became famous after racing an aircraft to New York City carrying newsreels of Charles Lindbergh's return to the United States after his transatlantic flight in 1927. In the late 1930s, No. 460 was operated by the Long Island Rail Road, and by the Pennsylvania-Reading Seashore Lines in the early 1950s, before being retired in 1953. No. 460 is the only surviving locomotive of its class and was listed on the U.S. National Register of Historic Places in 1979. From 2010 to 2016, No. 460 underwent cosmetic restoration at the Railroad Museum of Pennsylvania.
Pennsylvania Railroad 7002 is a class "E7s" 4-4-2 "Atlantic" type steam locomotive built for the Pennsylvania Railroad by their own Altoona Works in August 1902. Today, it is on display at the Railroad Museum of Pennsylvania outside of Strasburg, Pennsylvania in the United States. Originally No. 8063, the PRR renumbered it to No. 7002 after the original, claimed to be a land-speed-record-setter, was scrapped. It is the only survivor of its class and was listed on the National Register of Historic Places in 1979.
A duplex locomotive is a steam locomotive that divides the driving force on its wheels by using two pairs of cylinders rigidly mounted to a single locomotive frame; it is not an articulated locomotive. The concept was first used in France in 1863, but was particularly developed in the early 1930s by the Baldwin Locomotive Works, the largest commercial builder of steam locomotives in North America, under the supervision of its then chief engineer, Ralph P. Johnson.
Pennsylvania Railroad 5550 is a mainline duplex drive steam locomotive under construction in the United States. With an estimated completion by 2030, the locomotive will become the 53rd example of the Pennsylvania Railroad's T1 steam locomotive class and the only operational locomotive of its type, as well as the largest steam locomotive built in the United States since 1952. The estimated cost of PRR 5550 was originally $10 million, but an updated projected cost of $7 million was released with the acquisition of an existing long-haul tender from the Western New York Railway Historical Society in August 2017. Construction began in 2014 with the casting of the locomotive's keystone-shaped number plate. As of February 2024 the locomotive was 43% complete.
The Pennsylvania Railroad's class K29s comprised a single experimental 4-6-2 "Pacific" type steam locomotive. Constructed by Alco-Schenectady, it was given road number 3395. Although only one demonstrator was constructed, the K29s would become the basis for the highly successful K4s Pacifics and L1s Mikados. The lone example spent most of its life on the PRR's Pittsburgh division main line and was retired around 1929.
