The Pennsylvania Railroad invested in diesel locomotives from all major manufacturers until EMD finally "won out" in the first generation diesel wars.
What follows is a timeline of diesel locomotive purchases by brand.
Models in bold are represented in the author's collection.
| Alco | Baldwin | EMD | Fairbanks Morse | General Electric |
|
| 1937 | SW | ||||
| 1938 | |||||
| 1939 | |||||
| 1940 | |||||
| 1941 | NW2 | ||||
| 1942 | |||||
| 1943 | VO 660 | ||||
| 1944 | |||||
| 1945 | VO 1000 | SW1 | |||
| 1946 | E7 | ||||
| 1947 | PA-1 S-1 |
DR 12-8-3000 "Centipede" |
F3 | ERIE-Built | |
| 1948 | RS-1 | DR 6-4-2000 "Passenger Shark" DS 4-4-660 DS 4-4-1000 |
H10-44 | 44 Ton | |
| 1949 | DR 4-4-1500 "Shark" DRS 4-4-1000 |
F7 | H20-44 | ||
| 1950 | RS-2 S-2 |
DS 4-4-750 | E8 SW7 |
CFA 16-4 "C-Liner" |
|
| 1951 | FA-1 FA-2 RS-3 S-3 S-4 |
RF16 "Shark" S-12 RS-12 AS-616 RT-624 |
GP7 SW9 |
||
| 1952 | RSD-5 | FP7 | H12-44 H16-44 |
||
| 1953 | SD7 | ||||
| 1954 | |||||
| 1955 | GP9 | ||||
| 1956 | RS-11 RSD-7 RSD-15 |
LWT12 | H24-66 "Trainmaster" |
||
| 1957 | SD9 | ||||
| Last Steam Locomotives Retired | |||||
| 1958 | RSD-12 T-6 |
SW1200 | |||
| 1959 | |||||
| 1960 | |||||
| 1961 | |||||
| 1962 | RS-27 | U25B | |||
| 1963 | C424 | GP30 | |||
| 1964 | C425 | GP35 | |||
| 1965 | C628 | SD35 | U25C | ||
| 1966 | C630 | SD40 SD45 |
U28C | ||
| 1967 | U30C | ||||
| 1968 | C636 | U33C | |||
