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ALCO S 1 and S 3

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Power type  Diesel
AAR wheel arr.  B-B
Total produced  543 (S-1) 300 (S-3)
ALCO S-1 and S-3
Builder  American Locomotive Company Montreal Locomotive Works
Build date  April 1940–June 1950 (S-1) February 1950–November 1953 (S-3)
Gauge  4 ft 8 ⁄2 in (1,435 mm)

The ALCO S-1 and S-3 were 660 horsepower (490 kW) switcher diesel-electric locomotives produced by ALCO and their Canadian subsidiary Montreal Locomotive Works (MLW). Basically, the two locomotives differed only in trucks, with the S-1 using ALCO's own Blunt trucks, and the S-3 riding on standard AAR type A switcher trucks. The S-1 was built between April 1940 and June 1950, with a total of 543 completed, while the S-3 was constructed between February 1950 and November 1953 (MLW until 1957) with total sales of 300. A modified version, the S-10, was built by MLW only; 13 were built between January and June 1958.



The S-1 and S-3 are distinguishable externally from the very similar S-2 and S-4 1,000 horsepower (750 kW) switchers in that they have a smaller exhaust stack with a round base and a smaller radiator shutter area on the nose sides. The S-1/S-3 radiator shutter area is taller than it is wide, while the S-2/S-4 radiator area is wider. The smaller stack is due to the lack of turbocharging.

The S-10 is not externally distinguishable from later Canadian-built S-3 locomotives; it differed mostly in electrical equipment.

Original owners

The S-1 and S-3 models were sold to an extensive list of railroads and industrial operators, as detailed below. Major owners of the S-1 included the New York Central Railroad (NYC), with 71 locomotives; the New Haven with 65 locomotives; the L&N with 45 locomotives; the C&NW, with 29 locomotives; and the Pennsylvania Railroad (PRR) with 27 locomotives. Major customers for the S-3 included the CP, with 101; the CN, with 49; the NYC, with 43 locomotives; the B&M, with 16; and the PRR, with 13. The MLW S-10 was sold only to the CP.

The totals below include export orders and MLW-built locomotives.


ALCO constructed approximately 535 S-1s for the US market between 1940–1950. In addition, it produced a single S-1 for Canadian Car and Munitions (of Canada), five for Estrada de Ferro Central do Brasil in Brazil, five for Ferrocarriles Nacionales de México in Mexico, and five for the Steel Company of Wales in the United Kingdom.


ALCO and the Montreal Locomotive Works constructed approximately 300 S-3s for the North American market between 1950–1957. ALCO built 137; MLW built 163:


MLW constructed 13 S-10s, all for the Canadian Pacific Railway:


Numerous S-1 and S-3 locomotives remain in use, and several are preserved:

  • Ex-U.S. Army S-1 No. 7372 is at the Western Pacific Railroad Museum and painted in Western Pacific colors.
  • Ex-Canadian Pacific MLW S-3 No. 6568 is at the Saskatchewan Railway Museum.
  • References

    ALCO S-1 and S-3 Wikipedia