For most of its existence, the Pennsylvania Railroad was conservative in its locomotive choices and pursued standardization, both in locomotive types and their component parts.
Almost alone among U.S. railroads, the Pennsy designed most of its steam locomotive classes itself.
It built most of them at Altoona Works, outsourcing only when Pennsy facilities could not keep up with the railroad's needs.
In such cases, subcontractors were hired to build to PRR designs, unlike most railroads that ordered to broad specifications and left most design choices to the builder.

The Pennsy's favorite, outsourced locomotive builder was Baldwin Locomotive Works, which received its raw materials and shipped out its finished products on Pennsy lines.
The two companies were headquartered in the same city; Pennsy and Baldwin management and engineers knew each other well.
When the Pennsy and Baldwin shops were at capacity, orders went to the Lima Locomotive Works in Lima, Ohio.
Only as a last resort would the Pennsy use the American Locomotive Company (Alco), based in Schenectady, New York, which also built for Pennsy's rival, the New York Central.

The Pennsylvania Railroad had a design style that it favored in its locomotives.
One example was the square-shouldered Belpaire firebox.
This British-style firebox was a Pennsy trademark that was rarely used by other locomotive builders in the United States.
The Pennsy also used track pans extensively to retrieve water for the locomotive while in motion.
Using this system meant that the tenders of their locomotives had a comparatively large proportion of coal (which could not be taken on board while running) compared to water capacity.
Locomotives of the Pennsylvania had a clean look to them.
Only necessary devices were used and they were mounted neatly on the locomotive.
Smoke box fronts bore a round locomotive number board denoting a freight locomotive or a keystone number board denoting a passenger locomotive.
Otherwise the smoke box was uncluttered except for a headlamp at the top and a steam-driven turbo-generator behind it.
In later years the positions of the two were reversed, since the generator needs more maintenance than the lamp.

Each class of steam locomotive was assigned a class designation.
Early on this was simply a letter, but when these ran short the scheme was changed so that each wheel arrangement had its own letter, and different types in the same arrangement had different numbers added to the letter.
Sub-types were indicated by a lower-case letter; super-heating was designated by an "s" until the mid-1920s, by which time all new locomotives were super-heated.
A K4sa class was a 4-6-2 "Pacific" type (K) of the fourth class of Pacifics designed by the Pennsy.
It was super-heated (s) and was of the first variant type (a) after the original (unlettered).
Steam locomotives remained part of the Pennsy fleet until 1957.

The Pennsy's reliance on steam locomotives in the mid-20th century contributed to its decline.
Steam locomotives require more maintenance than diesel locomotives, are less cost efficient, and require more personnel to operate.
Like other railroads, the Pennsy was unable to update its roster at will during the World War II years; by the end of the war their roster was in rough shape.
In addition, the Pennsy was saddled with unsuccessful experimental steam locomotives such as the Q1, S1, and T1 "Duplex Drive" locomotives, and the S2 turbine locomotive.
Unlike most of their competition, the Pennsy did not acquire any Northerns or Berkshires.

Pennsy competitors managed this period better with their diesel locomotive rosters.
The Pennsylvania Railroad voluntarily preserved a roundhouse full of representative steam locomotives at Northumberland, Pennsylvania, in 1957 and kept them there for several decades.
These locomotives, with the exception of I1sa #4483 which is on display at Hamburg, New York, are now at the Railroad Museum of Pennsylvania in Strasburg, Pennsylvania.
In sharp contrast, the New York Central's Alfred E. Perlman deliberately scrapped all but two large, s
For most of its existence, the Pennsylvania Railroad was conservative in its locomotive choices and pursued standardization, both in locomotive types and their component parts. Almost alone among U.S. railroads, the Pennsy designed most of its steam locomotive classes itself. It built most of them at Altoona Works, outsourcing only when Pennsy facilities could not keep up with the railroad's needs. In such cases, subcontractors were hired to build to PRR designs, unlike most railroads that ordered to broad specifications and left most design choices to the builder.
The Pennsy's favorite, outsourced locomotive builder was Baldwin Locomotive Works, which received its raw materials and shipped out its finished products on Pennsy lines. The two companies were headquartered in the same city; Pennsy and Baldwin management and engineers knew each other well. When the Pennsy and Baldwin shops were at capacity, orders went to the Lima Locomotive Works in Lima, Ohio. Only as a last resort would the Pennsy use the American Locomotive Company (Alco), based in Schenectady, New York, which also built for Pennsy's rival, the New York Central.
The Pennsylvania Railroad had a design style that it favored in its locomotives. One example was the square-shouldered Belpaire firebox. This British-style firebox was a Pennsy trademark that was rarely used by other locomotive builders in the United States. The Pennsy also used track pans extensively to retrieve water for the locomotive while in motion. Using this system meant that the tenders of their locomotives had a comparatively large proportion of coal (which could not be taken on board while running) compared to water capacity. Locomotives of the Pennsylvania had a clean look to them. Only necessary devices were used and they were mounted neatly on the locomotive. Smoke box fronts bore a round locomotive number board denoting a freight locomotive or a keystone number board denoting a passenger locomotive. Otherwise the smoke box was uncluttered except for a headlamp at the top and a steam-driven turbo-generator behind it. In later years the positions of the two were reversed, since the generator needs more maintenance than the lamp.
Each class of steam locomotive was assigned a class designation. Early on this was simply a letter, but when these ran short the scheme was changed so that each wheel arrangement had its own letter, and different types in the same arrangement had different numbers added to the letter. Sub-types were indicated by a lower-case letter; super-heating was designated by an "s" until the mid-1920s, by which time all new locomotives were super-heated. A K4sa class was a 4-6-2 "Pacific" type (K) of the fourth class of Pacifics designed by the Pennsy. It was super-heated (s) and was of the first variant type (a) after the original (unlettered). Steam locomotives remained part of the Pennsy fleet until 1957.
The Pennsy's reliance on steam locomotives in the mid-20th century contributed to its decline. Steam locomotives require more maintenance than diesel locomotives, are less cost efficient, and require more personnel to operate. Like other railroads, the Pennsy was unable to update its roster at will during the World War II years; by the end of the war their roster was in rough shape. In addition, the Pennsy was saddled with unsuccessful experimental steam locomotives such as the Q1, S1, and T1 "Duplex Drive" locomotives, and the S2 turbine locomotive. Unlike most of their competition, the Pennsy did not acquire any Northerns or Berkshires.
Pennsy competitors managed this period better with their diesel locomotive rosters. The Pennsylvania Railroad voluntarily preserved a roundhouse full of representative steam locomotives at Northumberland, Pennsylvania, in 1957 and kept them there for several decades. These locomotives, with the exception of I1sa #4483 which is on display at Hamburg, New York, are now at the Railroad Museum of Pennsylvania in Strasburg, Pennsylvania. In sharp contrast, the New York Central's Alfred E. Perlman deliberately scrapped all but two large, s
Pennsylvania Railroad