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D&H 19 at Newtonville, April 1978 postcard.jpg
An ALCO/M-K PA-4 of the Delaware and Hudson Railroad in April 1978
Type and origin
Power typeDiesel-electric
BuilderPartnership of American Locomotive Company (ALCO) and General Electric (GE)
ModelPA, PB
Build dateJune 1946 –December 1953
Total produced297
Gauge4 ft 8 12 in (1,435 mm) standard gauge
1,600 mm (5 ft 3 in), Brazil
Length65 ft 8 in (20.02 m)
Loco weight306,000 lb (138,799 kg; 139 t)
Prime moverALCO 244 V16
Engine typeV16 Four-stroke diesel
Displacement10,688 cu in (175.14 l)
Traction motors4x GE 746 or 752 DC traction motors
Cylinder size9 in × 10 12 in (229 mm × 267 mm)
Loco brakeIndependent air.
Optional: Dynamic
Train brakesAir
Performance figures
Maximum speed117 mph (188 km/h)
Power output2,000 hp (1,490 kW) — PA-1/PB-1
2,250 hp (1,680 kW) — PA-2/PB-2
Tractive effort51,000 lbf (226.86 kN)
LocaleNorth America, Brazil
DispositionThree preserved, two under restoration, one converted to steam generator car, rest scrapped.

The ALCO PA was a family of A1A-A1A diesel locomotives built to haul passenger trains. The locomotives were built in Schenectady, New York, in the United States by a partnership of the American Locomotive Company (ALCO) and General Electric (GE) between June 1946 and December 1953. They were of a cab unit design, and both cab-equipped lead A unit PA and cabless booster B unit PB models were built.

Externally, the PA and PB models looked very similar to the ALCO FA models produced in the same period. Both the PA and FA models were styled by General Electric's Ray Patten. They shared many of the same characteristics both aesthetically and mechanically. It was the locomotive's mechanical qualities (the ALCO 244 V-16 prime mover) and newer locomotive models from both General Motors Electro-Motive Division (EMD) and General Electric (the partnership with ALCO was dissolved in 1953) that ultimately led to the retirement of the PA/PB locomotive model from revenue service. Six examples of PAs and PBs have been preserved in railroad museums.

ALCO's designation of P indicates that they were geared for higher speeds and passenger use, whereas the F designation marks these locomotives as being geared primarily for freight use. However, beyond this their design was largely similar - aside from the PA/PB's both being larger A1A-A1A types with an even more striking nose - and many railroads used FA and PA locomotives for both freight and passenger service.

Background and development[edit]

The PAs, as well as their cousins, the ALCO FAs, were born as a result of Alco's development of a new diesel engine design, the Model 244. In early 1944, development started on the new design, and by November 1945, the first engines were beginning to undergo tests. This unusually short testing sequence was brought about by the decision of Alco's senior management that the engine and an associated line of road locomotives had to be introduced no later than the end of 1946.

In preparation for this deadline, by January 1946, the first 16-cylinder 244 engines were being tested, and while a strike delayed work on the locomotives, the first two PA units were released for road tests in June 1946, for testing for one month on the Lehigh Valley Railroad. After these first tests were completed, the locomotives returned to the factory for refurbishment and engine replacement.

In September 1946, the first production units, an A-B-A set of PA1s in Santa Fe colors, were released from the factory, and sent to New York's Waldorf-Astoria Hotel, which had a private railroad siding, for exhibition before being launched into road service.[1]


Two models were offered: the 2,000 horsepower (1,500 kW) PA-1/PB-1 (built between September, 1946 and June, 1950); the 2,250 horsepower (1,680 kW) PA-2/PB-2 (built between April, 1950 and December, 1953)

Models popularly termed the PA-3/PB-3 were in fact only an upgrade of the PA-2/PB-2. The true PA-3/PB-3 model would have boasted 2,400 horsepower (1,800 kW), though none were ever built. Aside from the small power increase between the PA-1 and the PA-2, differences were minor. Externally PA-2s could be distinguished by the absence of the "eyebrow" trim piece on the grille behind the cab and the porthole window behind the radiator shutters. Internally, later PA-2 and PB-2 production featured a water-cooled turbocharger and other engine compartment changes, but these were frequently added to older models undergoing major repairs or overhauls. Four PA-1s were upgraded by Morrison-Knudsen in 1974-75 for passenger service on the Delaware & Hudson and became the PA4.[2] These were eventually used by Amtrak for the "Adirondack" train and then by the Massachusetts Bay Transit Authority before being sold to Mexico.

The cab and nose design profile of D&H Alco PA4 No. 18, returning from Morrison-Knudsen rebuild in 1975, as compared to that of an Amtrak EMD F unit.
Publicity photo of an ALCO PA-1 ABA set of the Santa Fe Railway in September, 1946.

Like its smaller cousin, the ALCO FA, the PA had distinctive styling, with a long, straight flat-tipped nose with a headlight in a square, slitted grille, raked windshields, and trim pieces behind the cab windows that lengthened and sleekened the lines. The overall design owed something to the Fairbanks-Morse Erie-built design, which had been constructed by ALCO's electrical equipment partner General Electric at their Erie, Pennsylvania plant. The majority of PA components were compatible with the FA.

Fans deemed the PA one of the most beautiful diesels and an "Honorary Steam Locomotive", as noted by Professor George W. Hilton in a book review in September, 1968 Trains Magazine. When accelerating, until the turbocharger came up to speed thick clouds of black smoke would pour from the exhaust stacks, due to turbo lag. Photographing a moving PA while smoking became a prime objective of railfans[3][4][5]

As with the FAs, the ALCO 244 V16 diesel prime mover proved to be the undoing of the PA: The engine had been rushed into production, and proved to be unreliable. The PA locomotives failed to capture a marketplace dominated by General Motors Electro-Motive Division and their E-units. The original Santa Fe three unit set #51L, 51A and 51B was repowered in August 1954 with EMD 16-567C engines rated at 1,750 hp (1,305 kW). This EMD repowering of the PAs was economically unfeasible and the remaining Santa Fe PAs retained their 244 engines.

Original owners[edit]

Railroad PA1 PB1 PA2 PB2 PA1 Road Numbers PB1 Road Numbers PA2 Road Numbers PB2 Road Numbers Notes
ALCO-GE Demonstrators 1 1 8375 8375B to New York Central Railroad 4212 and 4304
ALCO-GE Demonstrators 2 9077-9078 Demonstrated on Canadian National, painted in CN green and gold, later to Missouri-Kansas-Texas Railroad as PA-2s 59A,C. Last PA-1s built.
American Freedom Train (original) 1 1776 To Gulf, Mobile and Ohio Railroad 292
Atchison, Topeka & Santa Fe Railroad 28 16 51-62L,B, 70-73L 51-62A, 70-73A Four PA1s sold to Delaware & Hudson in 1967; became last to operate in U.S.
Denver & Rio Grande Western Railroad 4 2 6001, 6003, 6011, 6013 6002, 6012
Erie Railroad 12 2 850-861 862-863
Gulf, Mobile & Ohio Railroad 2 290-291
Lehigh Valley Railroad 14 601-614
Missouri-Kansas-Texas Railroad 4 8 57-58A,C 60-63A,C 59A,C were Alco PA-1 demonstrators rebuilt as PA-2s
Missouri Pacific Railroad 8 28 8001-8008 8009-8036 8011-8012 were originally owned by International Great Northern
New York, New Haven and Hartford Railroad 27 0760-0786 Unit 0783 to D&H in 1967 for parts.
New York, Chicago and St. Louis Railroad (Nickel Plate Road) 11 180-190
New York Central Railroad 4 4 4 4200-4203 4300-4303 4208-4211
Pennsylvania Railroad 10 5 5750-5759 5750B/5758B even #s
Pittsburgh and Lake Erie 4 2 4204-4207 4213-4214
St. Louis Southwestern Railway 2 300-301 To Southern Pacific Railroad 6067-6068
Southern Pacific Railroad (T&NO) 12 200-205A,B Renumbered to 200-211, then to Southern Pacific 6055-6066
Southern Pacific Railroad 12 6 27 7 6005-6010A,C 6005-6010B 6019-6045 5918-5924 6005-6010A,C renumbered to 6005-6016, 6005-6010B renumbered to 5910-5915
Southern Railway (CNO&TP) 6 6900-6905 Last PA's built by ALCO
Union Pacific Railroad 8 6 600-607 600B, 602B, 604B-607B One PA-1 converted for experimental coal-burning turbine
Wabash Railroad 4 1050-1053
São Paulo Railway, Brazil 3 600-602 1,600 mm (5 ft 3 in) gauge
Totals 169 39 81 8

Foreign sales[edit]

The PA-2 units sold to the 1,600 mm (5 ft 3 in) broad gauge Companhia Paulista de Estradas de Ferro of São Paulo State in Brazil were equipped with a bar pilot and solid horizontal steel pilot beam. One of these locomotives survives.

Surviving examples[edit]

Nickel Plate Road 190 at the Oregon Rail Heritage Center, where it is undergoing restoration

Five PA units and one converted PB unit survive.

  • One surviving unit, #600, is from the order of three broad gauge units sold to Companhia Paulista de Estradas de Ferro in Brazil. It exists at the Companhia Paulista Museum at Jundiai, São Paulo as a shell with no prime mover and no side panels. A restoration was begun in 2001 but has not been completed.
  • Four (No.16-19) are of the ex-Santa Fe group of locomotives purchased by the Delaware & Hudson in 1967. In 1974-1975, these four units were rebuilt for the D&H by Morrison-Knudsen and equipped with ALCO's 251V12 engines. During this rebuilding the units were given the designation PA-4 by MK. These locomotives were later sold to Mexico. Of the D&H units, two are in the United States, No.16 and No.18. These units returned to the U.S. in 2000 after years of storage at Empalme, Sonora, Mexico.
    • No.16, which was heavily damaged in a derailment while in Mexico, was planned to be cosmetically restored into its original "Warbonnet" colors for the Smithsonian Institution. The unit was acquired by the Museum of the American Railroad and transported to the museum's new site in Frisco, Texas in April 2011. This unit will be restored to full operational status as America's PA for use in special trains across the United States.[6]
    • No.19 is kept in operational condition at the National Museum of Mexican Railroad in Puebla, while No.17 remains on display in the museum. Unit DH-17 (former D&H #17) was painted in the classic Southern Pacific Daylight colors, but as of February 2010 had been painted over in primer.
  • Ex-Denver and Rio Grande PB-1 6002 was converted to a steam generator car in October 1965; it later gained Blomberg B trucks in 1980. It was sold to Ansco in late 1987 for service on the Ski Train, and later sold again in 2007 to the Algoma Central Railway.


  1. ^ Steinbrenner, Richard T (2003). The American Locomotive Company: A Centennial Remembrance. On Track Publishers. ISBN 0-911122-07-9.
  2. ^ See Anderson, Norman E. and MacDermott, C. G., "PA4 Locomotive." (Burlingame, Chatham Publishing Co.)(1978). ISBN 0896850358.
  3. ^ Ingles, J. David, Passenger Diesel Turned Legend, Trains Magazine January, 1997, p.54.
  4. ^ “Honorary steam locomotive” at Trains Magazine
  5. ^ Products, Marklin. "Märklin Product Database". Marklin Products. Retrieved 2009-05-26.
  6. ^

External links[edit]