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Baldwin "S-12" Locomotives: Specs, Roster, Data Sheet

Last revised: December 31, 2024

By: Adam Burns

The S-12 was an upgraded version of its predecessor, the S-8, although both models were cataloged at the same time.

Similar in size and mechanics, save for increased horsepower, this final switcher manufactured during the 1950s sold relatively well for Baldwin as numerous railroads and private industries purchased the model.

While the locomotive did have some complaints regarding reliability it was revered for its ability to out-pull nearly anything in its class (a Baldwin trademark thanks to their Westinghouse traction motors). 

The S-12 also saw the builder do away with the earlier complicated classification system and introducing one much simpler. Today, there are eight S-12's known to be preserved at museums while others are still hauling freight for short line carriers.  

Photos

Penn Central S-12 #8144 (ex-Pennsylvania #8784) is seen here in Charleston, West Virginia on the former New York Central in the fall of 1968. Fred Byerly photo. American-Rails.com collection.

Overview

Baldwin may have struggled as a diesel manufacturer but its switchers and road-switchers boasted good looks and clean lines, topped by a centered head-light on the long hood sporting decorative beveling. 

From a functionality standpoint they sat high and offered crews relatively good visibility on a modest frame.   The S-12 began production in 1951 and by that time was technically a product of the Baldwin-Lima-Hamilton Corporation (BLH).

BLH was formed through the merger of the Baldwin Locomotive Works and Lima-Hamilton in 1951 after the former came under the control of Westinghouse Electric Company, a long time supplier of internal components for Baldwin's diesels.

The two companies had collaborated on several electric locomotive projects over the years, dating all of the back to the 19th century.  Thanks to the S-12's increased horsepower it sold much better than its less powerful counterpart. 

Milwaukee Road S12 #912 (built as #1923) carries out switching chores at St. Paul Union Depot in April of 1968. Fred Byerly photo. American-Rails.com collection.

At 1,200 horsepower using Baldwin's latest prime mover, the 606A SC, railroads found the locomotive quite versatile in several applications from yard and industrial work to revenue service on secondary and branch lines. 

The locomotive came equipped with standard four axle (B-B) trucks and could produce a hefty 72,000 pounds of starting tractive effort (34,000 pounds continuous). 

Reception

When production had ended in August, 1956 the model had been sold to several railroads like the Chicago & North Western, Jersey Central, Southern Pacific, New York Central, Southern, and the ever-loyal Pennsylvania.

Additionally the military and industries purchased the locomotive including the Army, U.S. Steel, Armco Steel, American Smelting and Refining Company, Erie Mining, and others. In total, Baldwin sold 451 examples of the S-12.

Penn Central S12 #8337 (ex-PRR #8733) in Baltimore, Maryland; October 2, 1972. American-Rails.com collection.

The S-12 was certainly Baldwin's most popular switcher in terms of its horsepower rating and general reliability. This is a significant reason why the model continues to find use in short line service today, notably on short line SMS Lines which owns eight.

Data Sheet and Specifications

Production Roster

Total Built = 451

* First S-12 produced.

Preservation

The heritage of these locomotives includes:

• Michigan Limestone #116


• Tennessee Valley Authority #200


• U.S. Navy #65-00372


• Demonstrator #1200


• Southern Pacific #1547


• Erie Mining #7241


• Monongahela Railway #425


•  Great Northern #27. 

While four of these locomotives are operational, four are also used as a parts source.  Additionally, seven others can be found at museums:

• Patapsco & Back Rivers #345-#346


• Erie Mining #403


• New York Central #9313


• Southern Pacific #1550


• Texas & New Orleans (SP) #121


• Oliver Iron Mining #933

Kansas City Southern S-12 #1160 lays over in Kansas City, circa 1965. Photographer unknown. American-Rails.com collection.

Sources

• Foster, Gerald. A Field Guide To Trains. New York: Houghton Mifflin, 1996.

• 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.