Alco "S-3" Locomotives

Last revised: December 28, 2022

By: Adam Burns

The Alco S3 was the third model of switcher in its "S" line that the company produced. It was virtually identical to the previous S1 model that was built from 1940 through 1950 and its interesting that American Locomotive even elected to change the unit's name given their striking similarities.

The S3 design was not quite as successful as the S1, selling about half as many units. However, it was purchased by several Canadian lines through Alco's Montreal Locomotive Works located in Montreal, Quebec. 

The S1 was never offered in Canada while the S2 did witness several buyers, notably via Canadian National and Canadian Pacific.  This continued with the S3 as both Class I's acquired even more of that particular model.

Today, the S3 is perhaps the least preserved of the switcher series but several are extant.  At least three American-built examples are operational, Alexander Railroad #6 and #7 (of New York Central and Davenport, Rock Island & Western heritage) as well as Dardanelle & Russellville #18. In additional, several Canadian examples are preserved.


Classic car aficionados will surely enjoy this scene of Ford Motor Company S3 #6610 shunting a carload of new Mustangs (among a wide range of other cool models!) at its River Rouge Plant in Dearborn, Michigan circa 1965.


The Alco S3 model rolled into production in February, 1950, which was about four months before the final S1 rolled out of the builder's Schenectady, New York plant.

The model deviated a bit from its earlier counterpart in that it was equipped with the more standard AAR trucks, while the S1 and S2 designs featured Alco's very own Blunt trucks (the manufacturer was one of the only major builders of diesel locomotives to design its own trucks).

Like the S1, the S3 was a standard four-axle design featuring traction motors from General Electric and air components (brakes and compressors) from Westinghouse. Both featured dynamic braking, weighed 105 tons, and carried a length of just over 44 feet.

However, the S3 also differed in some other ways as well. While both models offered a continuous tractive effort rating of around 46,000 pounds the S3 featured more starting effort, 59,700 pounds (compared to the S1's 57,500 pounds).

Additionally, the most noticeable difference, internally, was that the S3 included 660 horsepower whereas the S1 was slightly less powerful at just 600 horsepower.

Most likely the S3 sold fewer units than the S1 for a few reasons; first, railroads were probably looking for a more powerful switcher, which was already available in the S2; and second, aside from the S2, those that wanted the extra power had a second chance at doing so with the S4 (which replaced the S2).

Data Sheet and Specifications

Entered Production2/1950 (Ford Motor Company #6605)
Years Produced2/1950-11/20/1953
Model SpecificationE1530A
Engine539, 6-Cylinder In-Line
Carbody StylingAlco
Length (Between Coupler Pulling Faces)45' 5.75"
Height Above Rail Head14' 6"
Weight210,000 Lbs.
Truck TypeGRS Rigid Bolster, Drop-Side Equalizer (AAR Type-A)
Truck Wheelbase8'
Wheel Size40"
Traction MotorsGE 731 (4)
Traction GeneratorGT553
Gear Ratio75:16
Tractive Effort Rating46,000 Lbs. at 5 MPH.
Top Speed60 MPH

During the course of production the S-3 switched from a short, to long-shank coupler so the locomotive could more easily negotiate curves while pulling a cut of cars.

The final short-shank variant appeared on La Salle Coke #4 (construction number 80986) on June 11, 1954.  In Canada the first switcher to feature a long-shank coupler was Canadian Pacific #6523 (construction number 80987) completed on January 17, 1955.

Production Rosters


Owner Road Number(s) Quantity Date Built
Aluminum Company Of America (Alcoa)811952
Ann Arbor Railroad4-741950
Boston & Maine1173-1188161950-1952
Brooks-Scanlon Corporation101-10221952
Champion Paper Company210411952
Chicago & North Western1262-126761951
Davenport, Rock Island & Northwestern1-771952-1953
Davison Chemical, W.R. Grace & Company10111951
El Dorado & Wesson Railway1811952
Ford Motor Company6605-661161950
Frederick Snare Corporation711951
General Portland Cement111951
Graysonia, Nashville & Ashdown Railroad5111951
Greater Portland Public Development Corporation66111950
Humble Oil & Refining Company99711950
Louisville & Nashville69-7571953
Maine Central961-96221953
Manistique & Lake Superior Railroad111950
Mount Hood Railroad5011950
New York Central874-916431950-1951
Solvay Processing211952
Southern Pacific1023-1032101951
Swift & Company66411951
Texas & Northern3-421952
Texas City Terminal3211950
Washington, Idaho & Montana Railway3011950
West Pittston-Exeter Railroad611950

Montreal Locomotive Works

Owner Road Number(s) Construction Number(s) Completion Date
Canadian National8484-849376433-764423/1954-6/1954
Canadian Arsenals1772805/1952
Bathurst Power & Paper3772811/1954
Essex Terminal103772826/1952
Canadian National8462-846877283-772891/1953-4/1953
Price Brothers106776349/1950*
Canadian Pacific6500-650577635-776404/1951-5/1951
National Harbours BoardD2-D477641-776436/1951
National Harbours BoardD5-D977752-777568/1951-10/1951
Canadian Pacific6506-651277757-7776811/1951-3/1952
Canadian Pacific6513-651779116-791206/1952-8/1952
Canadian National8469-848379129-791435/1953-11/1953
Canadian Pacific6518-652279164-791689/1953-10/1953
Canadian National8494-849880981-809856/1954-8/1954
La Salle Coke4809866/1954
Canadian Pacific6523-652680987-809901/1955
Canadian Pacific6527-653581072-810802/1955-3/1955
Canadian Pacific6536811713/1955
Canadian Pacific6537-654781193-812037/1955-8/1955
Canadian Pacific6548-655781505-815143/1956-4/1956
Canadian Pacific6558-656181545-815485/1956-6/1956
Canadian Pacific6562-657181663-816722/1957-3/1957
Canadian Pacific6572821583/1957
Canadian Pacific6573-660082159-821864/1957-9/1957

* First S-3 built by the Montreal Locomotive Works.  It wore "Canadian Pacific #7004" as a demonstrator.


  • Foster, Gerald. A Field Guide To Trains. New York: Houghton Mifflin, 1996.
  • Kirkland, John F. Diesel Builders, The:  Volume Two, American Locomotive Company And Montreal Locomotive Works. Glendale: Interurban Press, 1989.
  • Pinkepank, Jerry A. Diesel Spotter's Guide.  Milwaukee: Kalmbach Publishing Company, 1967.
  • Solomon, Brian. Alco Locomotives. Minneapolis: Voyageur Press, 2009.

Ann Arbor S3 #10 (ex-Manistique & Lake Superior #1) and a string of matching cabooses sit at the small yard in Owosso, Michigan during May of 1980. Note the poor condition of the track by this time. Rob Kitchen photo.


In the end the Alco S3 sold just 292 units. Interestingly, though, a wide range of railroads and industries purchased the model like the Pennsylvania, Chicago & North Western, Southern Pacific, Ann Arbor, New York Central, and others.

The Montreal Locomotive Works built S3s for Bathhurst Power & Paper, Canadian Arsenals, Canadian National, Canadian Pacific, Essex Terminal, LaSalle Coke, and National Harbours Board.

The MLW demonstrator was purchased by the Price Brothers (it was later picked up by CP). Overall, MLW constructed 163 S3's with CP and CN buying the majority of these (140). 

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