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Baldwin "RS-12" Locomotives

Last revised: June 1, 2023

By: Adam Burns

The RS-12 was Baldwin's lightest road-switcher design in terms of horsepower, featuring just 1,200 HP. 

As  John Kirkland notes in his book, "The Diesel Builders: Volume Three (Baldwin Locomotives Works)," Eddystone never made a concerted effort to challenge Alco's success in this market with its popular RS-1.

Baldwin had a built a few 1,000 horsepower road-switchers (DRS-4-4-1000) for a few North American lines (Tennessee Central, Canadian Pacific, and Pennsylvania) but by and large stayed out of the market.

When the company upgraded its road-switchers with the 608A prime mover, it increased the DRS-4-4-1000 by 200 horsepower and renamed it the RS-12.  

Baldwin put more effort into marketing this new variant but by the 1950s railroads were looking for greater power in an over-the-road locomotive.  As such, the RS-12 saw few sales.

Today, there are several RS-12's preserved, most of Seaboard Air Line heritage; in addition, McCloud River Railroad #33 (only one of two built with dynamic brakes) can be found at California's popular Skunk Train while short line freight carrier Escanaba & Lake Superior owns eight units (all of Seaboard heritage).


Pennsylvania RS12 #8105. Author's collection. This unit was part of a batch of six (#8105-8110) to initially feature the high, short hood. This group did not feature dynamic brakes. In his book, "The Diesel Builders: Volume Three (Baldwin Locomotives Works)," John Kirkland notes the following: "As a consequence of carbody design changes that were made beginning in 1953 on the 1,600 hp road switcher models...certain changes were also made to the model RS-12 production beginning in 1954 in order to permit using the same jigs and fixtures for all road switcher production insofar as was possible. To accomplish this objective, the underframes were lengthened from 58 feet to 58'6" over couplers, and the level of the short hood was raised nearly to the level of the cab roof. The long hood, however, was not raised..."


The RS12 was Baldwin's lone light road-switcher the builder attempted to market although it appears to have been largely a half-hearted effort. 

Incidentally, Baldwin's success in the diesel market began with a line of switchers and it had been producing small electric locomotives, such a various box cab designs, for years in conjunction with Westinghouse.

The RS12 was one of four road switcher models Baldwin-Lima-Hamilton offered in its new Standard line released in 1950.

These new locomotives sold far better than the company's earlier designs of the 1940s and one cannot help but wonder how successful BLH would have become had parent Westinghouse allowed it to continue refining its diesels.

9o627461788926899837904859.jpgMilwaukee Road RS12 #926 (built as #970) is seen here at Pigs Eye Yard in St. Paul, Minnesota during June of 1968. Fred Byerly photo. American-Rails.com collection.

In any event, BLH's new classification system was fairly straightforward and certainly much easier to decipher than its earlier system, partially based from the steam era.

In the case of the RS12 the "RS" referred to Road Switcher while the "12" regarded its 1,200 horsepower (the model was actually even easier to understand than the AS16, AS416, and AS616 classifications).

New York Central RS-12 #6225 (built as #5825) leads a two-coach commuter run northbound on the Putnam Division as the train crosses Croton Lake (New York), circa 1957. Meyer Pearlman photo. American-Rails.com collection.

The RS12 began production in April of 1951 and utilized Baldwin's 608A prime mover, an upgraded version of a previous engine.  The locomotive featured a B-B truck setup (meaning there were two axles per truck) but no dynamic braking.

As with all of Baldwin's road switchers the RS12 used its standard carbody design; a short lead hood, offset cab, and trailing long hood. The look was actually quite pleasing with soft beveling and a flush roof line.

Overall, the RS12 was 58 feet in length and weighed in at a very light 133 tons (for a locomotive of its size). While rather long and light for its horsepower rating the locomotive included a starting tractive effort of 60,000 pounds and 32,000 pounds continuous.

934867237423638749862693807.jpgPennsylvania DRS-4-4-1000 #9277 is seen here at Camden, New Jersey, circa 1965. American-Rails.com collection.

DRS-4-4-1000 Roster

Owner Road Number Baldwin Serial Number Construction Number Completion Date
Tennessee Central751737067/13/1948
Tennessee Central762737077/13/1948
Tennessee Central773737088/3/1948
Canadian Pacific80004739671/21/1949
Canadian Pacific80015739681/19/1949
Canadian Pacific80026739691/11/1949
Canadian Pacific80037739701/26/1949
Canadian Pacific80048739711/27/1949
Canadian Pacific80059739721/25/1949
Canadian Pacific800610739731/25/1949
Canadian Pacific800711739742/28/1949
Canadian Pacific800812739752/21/1949
Canadian Pacific800913739762/3/1949
Canadian Pacific801014739772/9/1949
Canadian Pacific801115739782/10/1949
Canadian Pacific801216739792/11/1949

Data Sheet and Specifications

Entered Production4/3/1951 (Pennsylvania #8975)
Years Produced4/3/1951 - 5/15/1956
Baldwin ClassDRS-4-4-1200/1 SC
Engine BuilderDe La Vergne
Carbody StylingBaldwin
Length (Between Coupler Pulling Faces)58'
Weight325,000 Lbs
Height (Top Of Rail To Top Of Cab)14'
Width10' 2"
Truck TypeGSC Swing Bolster, Drop Side Equalizers
Truck Wheelbase9' 10"
Wheel Size42"
Traction Motors362DF (4)*, Westinghouse
Traction Generator480FZ, Westinghouse
Auxiliary GeneratorYG42B, Westinghouse
Gear Ratio14:68
Tractive Effort Rating32,400 Lbs at 11.4 mph
Top Speed60 MPH

* Late variants were equipped with 362DZ model traction motors.

During the course of production there were several changes made to the RS-12, as is described in the following:

  • New York Central #5820-5836: Equipped with steam generators for passenger service and MU capability.

  • Pennsylvania #8105-8110: Frame length increased from 58' to 58' 6" (over couplers) and the short hood raised to nearly the height of the cab roof.

  • Kaiser Bauxite #101-104 and McCloud River Railroad #32-33: Equipped with 370DEZ traction motors with 15:63 gearing which increased continuous tractive effort to 48,000 Lbs at 7.6 mph.

Production Roster

Total Built = 50

Owner Road Number Baldwin Serial Number Construction Number Completion Date
Chicago, Milwaukee, St. Paul & Pacific (Milwaukee Road)9702752425/14/1951
New York Central582037525611/7/1951
New York Central582147525711/7/1951
New York Central582257525811/9/1951
New York Central582367525911/9/1951
New York Central582477526011/12/1951
New York Central582587526111/12/1951
New York Central582697526211/13/1951
New York Central5827107526311/13/1951
New York Central5828117526411/20/1951
New York Central5829127526511/20/1951
New York Central5830137526612/19/1951
New York Central5831147526712/19/1951
New York Central5832157526812/21/1951
New York Central5833167526912/21/1951
New York Central5834177527012/27/1951
New York Central5835187527112/31/1951
New York Central5836197527212/31/1951
Seaboard Air Line146620754755/13/1952
Seaboard Air Line146721754765/19/1952
Seaboard Air Line146822754775/21/1952
Seaboard Air Line146923754785/22/1952
Seaboard Air Line147024754795/22/1952
Seaboard Air Line147125754805/24/1952
Kaiser Bauxite Company10126754864/30/1952
Kaiser Bauxite Company10227754874/30/1952
Chicago, Milwaukee, St. Paul & Pacific (Milwaukee Road)871297570210/30/1952
Central Railroad Of New Jersey120630754461/30/1953
Central Railroad Of New Jersey120731754471/30/1953
Central Railroad Of New Jersey120832754481/30/1953
Central Railroad Of New Jersey120933756981/30/1953
Seaboard Air Line147234757651/8/1953
Seaboard Air Line147335757661/8/1953
Seaboard Air Line147436757671/12/1953
Seaboard Air Line147537757681/16/1953
Durham & Southern120044760013/26/1954
Durham & Southern120145760023/31/1954
Durham & Southern120246760033/30/1954
McCloud River Railroad3247760244/29/1955
McCloud River Railroad3348761054/29/1955
Kaiser Bauxite Company10349761335/15/1956
Kaiser Bauxite Company10450761345/15/1956


  • Kirkland, John F. Diesel Builders, The:  Volume Three, Baldwin Locomotive Works. Pasadena: Interurban Press, 1994.
  • Pinkepank, Jerry A. Diesel Spotter's Guide.  Milwaukee: Kalmbach Publishing Company, 1967.
  • Solomon, Brian.  Baldwin Locomotives.  Minneapolis:  Voyageur Press, 2009.

California Western RS12 #56 (built as McCloud River Railroad #33) lays over at the engine shop in Willits, California in May, 1973. Author's collection.

The New York Central would come to own the most, seventeen, which interestingly were supposed to be model LRS-1200s from Lima. However, due to the Lima-Baldwin merger NYC accepted the RS12 model instead. 

In total, eight railroads purchased the locomotive; the aforementioned NYC and McCloud River as well as the Milwaukee Road, Jersey Central, Durham & Southern, Kaiser Bauxite, Seaboard Air Line, and ever-loyal Pennsylvania. 

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