ALCO S-2 and S-4

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ALCO S-2 and S-4
GU 1001 S4.jpg
Grafton and Upton Railroad #1001, an S-4, rests in Hopedale, MA on 11 May 2008
Type and origin
Power typeDiesel-electric
BuilderALCO and MLW
ModelS-2 and S-4
Build dateS-2: August 1940 (1940-08) – June 1950 (1950-06)
S-4: June 1949 (1949-06) – August 1957 (1957-08)
Total producedS-2: 1502, S-4: 797
Gauge4 ft 8+12 in (1,435 mm) standard gauge
TrucksS-2: Blunt
S-4: AAR type A
Wheel diameter40 in (1,016 mm)
Minimum curve50° or 118.31 ft (36.06 m)
Wheelbase30 ft 6 in (9.30 m)
Length46 ft (14.02 m)
Width10 ft 2+12 in (3.11 m)
Height14 ft 6 in (4.42 m)
Loco weight230,000 lb (100,000 kg)
Fuel capacity635 US gal (2,400 L; 529 imp gal)
Prime moverAlco 539T
Engine typeInline 6 Four-stroke diesel
Displacement1,595 cu in (26.14 L) per cylinder
9,572 cu in (156.86 L) total
GeneratorGE GT 553-A
Traction motors(4) GE 731
Cylinder size12+12 in × 13 in (318 mm × 330 mm)
Performance figures
Power output1,000 hp (746 kW) @ 740 rpm
Tractive effort57,500 lb (26,100 kg)
LocaleUnited States, Canada, Mexico, Australia

The ALCO S2 and S4 were 1,000-horsepower (746 kW) diesel electric switchers produced by ALCO and Canadian licensee Montreal Locomotive Works (MLW).

Powered by turbocharged, 6-cylinder ALCO 539 diesel engines, the two locomotives differed mainly in their trucks: the S-2 had ALCO "Blunt" trucks; the S-4, AAR type A switcher trucks. A total of 1,502 S-2s were built from August 1940 to June 1950; 797 S-4s were built from June 1949 to August 1957. The S-4 was first produced in Canada, with ALCO production beginning in August 1950.

A modified version, the S-7, was built by MLW only; 29 were built between June and August 1957.


The locomotives' exterior was styled by Alco engineer Ray Patten, who used curves in a mild application of Art Deco principles.[1]


The S-2 and S-4 are distinguishable externally from the very similar S-1 and S-3 660 hp (492 kW) switchers in that they have a larger exhaust stack with an oblong base and a larger 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 larger stack is due to turbocharging. The carbody and cab of late S-2s are nearly indistinguishable from those of S-4s. Hence, a truck swap can cause many to misidentify a unit.[original research?]


A few S-2s and S-4s are still in service on shortline railroads around the United States. Several more are preserved in U.S. and Canadian railroad museums.

An S-2 of D&RGW heritage survives on the Big South Fork Scenic Railway, as number 102. It was purchased in February 1964 for the Kentucky and Tennessee Railway, and is in operable condition in Stearns, Kentucky. This was one of the diesels that replaced Southern 2-8-2 #4501 on the K&T.

Southern Pacific 1474 is in operation, in rotation, at the Orange Empire Railway Museum in Perris, California, pulling a tourist train on weekends.

Western Pacific 563, one of two S-4s purchased by that railroad, is today preserved at the Western Pacific Railroad Museum at Portola, California.

Fore River Transportation had one S-4 in a derelict state being used for parts until it was scrapped in 2011.

New York, Susquehanna and Western Railway S-2 #206 sits cosmetically restored at Maywood Station in Maywood, New Jersey.[2]

The Cooperstown and Charlotte Valley Railroad operates a pair of restored ex-Canadian National units S-4 #3051 (formally CN #8181) and S-7 #3052 (formally CN #8223). In 2017, they had acquired the former Concord and Claremont Railroad ALCO S-4 units S-4 #102 (formally D&H #3050) and S-4 #104 (formally D&H #3036). As of 2020, all but #104 were operational on the tourist passenger and maintenance of way services between Milford and Cooperstown, New York. S-7 #3052 is thought to be the last S-7 built that is still in operation.

In Muskogee, Oklahoma, at the Three Rivers Museum ,a S-2 #63-138 sits behind the Midland Valley Station.

The Houston Railroad Museum in Houston, Texas, has two S-2s: ex-Santa Fe #2350 and ex-Houston Belt and Terminal #14.

ALCO S-2 #224 CYDZ (Conrad Yelvington Distributors) in Orlando-FL

Conrad Yelvington Distributors, an aggregate supplier in Orlando, Florida, owns a former Chesapeake & Ohio (C&O) S-2, now numbered 224. Though not used as often as their EMD SW9 number 2112, the unit is operational.

The Florida Railroad Museum in Parrish uses ex-Conrad Yelvington ALCO S-2 #251 as a backup engine on their weekend train rides.

Louisville & Nashville rebuilt many of their Alco switchers with 12-567 EMD prime movers in an effort to standardize their switching fleet. One of these, S-4 (or S-4m as rebuilt) #2326 survives at Gerdau Ameristeel in Cartersville, GA. Ameristeel recently donated the locomotive to the Southeastern Railway Museum at Duluth, GA.

The Oil Creek and Titusville Railroad operates S-2s #75 and #85 on its tourist/freight railroad.

The Virginia & Truckee Railroad acquired an S-4 from PPL Montana in 2010. The locomotive is in operable condition and slowly being repainted to the railroad's diesel colors.

The Toledo, Lake Erie, and Western owns four ALCO S-2 and S-4s. TLEW 62, a S-2 purchased in 2012, ex. Delray Cement 62, TLEW 112, a S-2 that was part of the original TLEW roster, now reduced to a parts unit as of 2010, TLEW 5109, a S-4, and the only operating ALCO on the line currently. 5109 recently was repainted into its original Chesapeake and Ohio colors in September 2013. TLEW 5109's horn was stolen during the repainting process. TLEW 9752, a S-4 of Penn Central and Pittsburgh & Lake Erie heritage, was not used much, and was eventually scrapped for parts in October 2010.

Heritage Cooperative in Mechanicsburg, Ohio, is the latest in a string of owners for the former Baltimore & Ohio 9040, an operating S-2 that retains her second B&O number. She was built as B&O 496 in 1945.

An S-2 built in 1946 was serving the Columbia & Reading Railway as #2-26 in Columbia, Pennsylvania, during 2019 after first operating on the C&O as #5015 and later on six other railroads.[3]

ALCO S-2 in a railroad museum in Alabama

The North Alabama Railroad Museum in Huntsville, Alabama runs an S-2 in regular tourist excursions, Mercury & Chase #213. It also owns another S-2, Mercury & Chase #484, which returned to service with #213 in 2018. The museum also has ex-Santa Fe #1534, an S-4.

The San Francisco Bay Railroad, the short-line railroad for the Port of San Francisco, operates S-2s #23 and #25 from the San Francisco Belt Line Railroad.

In the mid-1960s, Hamersley Iron purchased an S-2 for use in the Pilbara region of Western Australia.[4]

The coal-hauling Beech Mountain Railroad in Alexander, West Virginia, rosters an S-2 (#113) and an S-4 (#115). Both were built new for Michigan Limestone and Chemical Company.

ADMX Alco S-2 "E'Ville" 1 sits in CSX Transportation's Howell Yard in Evansville, Indiana, October 2016. This unit has since been scrapped.

ADMX "E'Ville" 1 (Ex-MRS 210) was on static display in Evansville, Indiana, near CSX Transportation's Howell terminal. ADM scrapped it in early Fall of 2017.

The Minnesota, Dakota and Western Railway in northern Minnesota uses S-2s to serve a Boise paper mill on the Canadian National line.

See also[edit]


  1. ^ "Locomotives-Canadian Pacific 7020". Toronto Railway Historical Association. 2001–2014. Retrieved 30 August 2014.
  2. ^ "Archived copy". Archived from the original on 26 May 2009. Retrieved 2 June 2009.CS1 maint: archived copy as title (link)
  3. ^ (1) Harwood, Herbert H. Jr. (April 2000). Rails to the Blue Ridge: The Washington and Old Dominion Railroad, 1847 – 1968 (PDF) (3rd ed.). Fairfax Station, Virginia: Northern Virginia Parks Authority. p. 137. ISBN 0615114539. LCCN 77104382. OCLC 44685168. Archived from the original (PDF) on 28 September 2017. Between 1959 and 1968 the W&OD leased various C&O Alco S-2 1000 hp switchers, specifically C&O Nos. 5000 (9160), 5006 (9162), 5009, 5011, 5012, 5015, and 5102. In Appendix K of Northern Virginia Regional Park Authority - Pre-filed Direct Testimony of Mr. Hafner, Mr. Mcray and Mr. Simmons, 30 November 2005 (Part 5), Case No. PUE-2005-00018, Virginia State Corporation Commission. Obtained in "Case Docket Search". Virginia State Corporation Commission. Retrieved 28 September 2017.
    (2) k41361 (24 February 2010). "Columbia & Reading S2.AVI". Archived from the original (video) on 29 June 2016. Retrieved 29 June 2016. Video of CORY 2-26 crossing Route 262 in Columbia, Pennsylvania.
    (3) Walker, Craig (27 September 2013). "Columbia & Reading ALCO S2 CORY 2-26". RailPictures.Net. Columbia, Pennsylvania. Archived from the original on 4 June 2015. Retrieved 28 January 2014. Tucked away in a scrap yard in Columbia, Pennsylvania, is Columbia & Reading S2 2-26. This 1946-built Alco has put in the miles for a number of railroads, starting with the Chesapeake & Ohio (#5015, then #9165) followed by stints as GEX 106, FCIN 106, PVRR 27, CCCR 27 and JCNX 27.
    (4) Painter, Kevin (13 February 2019). "CORY 2-26(S2)". Pictures of CORY 2-26. Columbia, Pennsylvania: RR Pictures Archive.Net. Retrieved 7 June 2019.
  4. ^ Exhibits Pilbara Railway Historical Society
  • Dorin, Patrick C. (1972). Chicago and North Western Power. Burbank, California: Superior Publishing. p. 136. ISBN 0-87564-715-4.
  • Pinkepank, Jerry A. (1973). The Second Diesel Spotter's Guide. Kalmbach Publishing Co., Milwaukee, WI. p. 224. ISBN 0-89024-026-4.
  • Toppan, Andrew et al. Alco/MLW S-2 Roster. Retrieved on 29 December 2005.
  • Toppan, Andrew et al. Alco/MLW S-4 Roster. Retrieved on 29 December 2005.
  • Steinbrenner, Richard T. (2003). The American Locomotive Company: A Centennial Remembrance. On Track Publishers LLC, New Brunswick, NJ. ISBN 0-911122-07-9.