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Alco "C-420" Locomotives

Last revised: June 10, 2023

By: Adam Burns

American Locomotive's first new Century models was the C420. It was a four-axle design that offered sufficient horsepower.

However, to some extent Alco continued to catalog custom models when a universal design would have sufficed, such as what EMD and General Electric had been doing for years.

As John Kirkland points out in his book, "The Diesel Builders: Volume Two," it was essentially an extension of the earlier RS32.  Its specification became DL721A whereas the RS32 had been DL721.

The C420 was meant to be a less powerful version of the C424, which was being produced at the same time. The Alco C420 had modest sales but the first design of the Century series did little to improve Alco's standing in the locomotive manufacturer's race. 

On a broader perspective, the C420 did prove one of Alco's more successful in the Century line and could be found on numerous railroads. 

Interestingly, despite lukewarm sales, several C420s are preserved today.  In addition, a handful even remain in freight service at various short lines around the country. 


A pair of Lehigh Valley C420's and other Alco's roll through the west end of Allentown Yard during the 1970s; Allentown, Pennsylvania. American-Rails.com collection.


The Alco C420 used the builder's new 261C prime mover that was much more reliable over its earlier designs.

The model began production in June of 1963 and as was the case with late RS designs, the C420 featured a standard low nose (high nose units were built on request), similar to the Standard Cab design first employed by EMD on its GP30 model.

As the designation suggests (which was a completely new system unveiled by Alco whereby the "C" stood for Century, "4" regarded the number of axles, and "20" referred to the horsepower), the C420 was capable of producing 2,000 horsepower and found buyers among a number of Class I railroads.

Interestingly, the largest buyer of C420s was the Pennsylvania-owned Long Island Rail Road, which owned thirty.


Once again, the C420 was more of a reactionary release by Alco in an attempt to remain competitive with newcomer General Electric and its U25B which debuted in 1959.

It's rather unfortunate that by the early 1960s Alco was generally looked upon with resignation by the industry as the Century series, particularly the four axle models, were quite adept locomotives which were very reliable. Additionally, they continued to offer incredible pulling power (an Alco trademark) and fuel efficiency.

Surprisingly, despite GE now being an Alco competitor, the Schenectady manufacturer continued to purchase from its one-time ally internal components as it always had such as traction motors and generators.

02934273475627862896989070978.jpgLehigh Valley C420 #410 is seen here at the engine terminal in Oak Island, New Jersey, circa 1970. Photographer unknown. American-Rails.com collection.

From a technical standpoint the C420 was meant to replaced the RS32 model and while it offered less starting tractive effort (57,200 pounds) provided more continuous effort (38,000 pounds).

Interestingly, neither Alco nor GE sold many models during the mid-1960s as EMD was once again dominated the market with its 2,500 horsepower GP35 of 1963 (which would go on to sell well over 1,000 examples).  By the time production had ended in 1968 only a little over 100 Alco C420s had been built.

However, aside from the large Class Is who purchased the model several smaller lines did as well such as the Piedmont & Northern, Tennessee Central, Lehigh & Hudson River, Erie Mining, Mississippi Export, and even the Secratario de Communicaciones Y Transportes of Mexico.

Data Sheet and Specifications

Entered Production6/1963 (Lehigh & Hudson River #21)
Years Produced6/1963-8/8/1968
Model SpecificationDL721A
Engine251C, V-16
Carbody StylingAlco
Length (Between Coupler Pulling Faces)60' 3"
Weight250,000 Lbs.
Dynamic BrakesOptional
Truck TypeSwing Bolster, Drop-Side Equalizer (AAR Type-B)
Truck Wheelbase9' 4"
Wheel Size40"
Traction MotorsGE 752 (4)
Traction GeneratorGT581
Steam GeneratorOptional
Gear Ratio64:19 (80.5 MPH), 79:24 (82.5 MPH)
Tractive Effort Rating57,200 Lbs.
Top Speed82.5 MPH

Production Roster

Total Built = 131

Owner Road Number(s) Serial Number(s) Date Built
Erie Mining Company 600-602 3437-01 thru 3437-03 12/1965
Lehigh & Hudson River 21, 22 84720, 84721 6/1963
Lehigh & Hudson River 23, 24 3431-01, 3431-02 12/1965
Lehigh & Hudson River 25, 26 3431-03, 3431-04 1/1966
Lehigh & Hudson River 27-29 3463-01 thru 3463-03 7/1966
Lehigh Valley 404-415 3385-01 thru 3385-12 10/1964
Long Island Rail Road 200-203 84722-84725 12/1963
Long Island Rail Road 204 84726 1/1964
Long Island Rail Road 205-207 84727-84729 2/1964
Long Island Rail Road 208 84779 2/1964
Long Island Rail Road 209, 210 84780, 84781 3/1964
Long Island Rail Road 211-214 84782-84785 4/1964
Long Island Rail Road 215-220 84786-84791 5/1964
Long Island Rail Road 221 3384-01 7/1964
Long Island Rail Road 222-229 6006-01 thru 6006-08 8/1968
Louisville & Nashville 1300-1305 3370-15 thru 3370-20 6/1964
Louisville & Nashville 1306-1313 3467-01 thru 3467-08 8/1966
Louisville & Nashville 1314, 1315 3467-09, 3467-10 9/1966
Mississippi Export 63 3425-01 9/1965
Monon Railroad 501, 502 (featured high, short hoods that housed steam generators) 3448-05, 3448-06 8/1966
Monon Railroad 503-506 3448-01 thru 3448-04 8/1966
Monon Railroad 507-518 3490-01 thru 3490-12 8/1967
New York, Chicago & St. Louis (Nickel Plate Road) 578 84792 6/1964
Norfolk & Western 413-420 3397-01 thru 3397-08 12/1964
Piedmont & Northern 2000, 2001 3430-01, 3430-02 12/1965
Seaboard Air Line 110-113 3418-01 thru 3418-04 5/1965
Seaboard Air Line 114-124 3418-05 thru 3418-15 6/1965
Seaboard Air Line 125, 126 3418-16, 3418-17 8/1965
Seaboard Air Line 127-135 3418-18 thru 3418-26 8/1965
Seaboard Air Line 136 3459-01 5/1966
Secretaría de Comunicaciones y Transportes (Mexico) 7123-10, 7123-11 3432-01, 3432-02 12/1965
Tennessee Central 400, 401 3438-01, 3438-02 1/1966, 2/1966


  • 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.

2937527352736792602987809278.jpgLong Island Rail Road C420 #206 was photographed here at the engine terminal in Jamaica, New York in 1964. At the time of this photo the locomotive was only a few months old. American-Rails.com collection.

Perhaps most fascinating with this model, in terms of its history, is how many continued to find usefulness in freight service long after they were sold by their original owner.

Today, close to 40 of this relics remain preserved with the most famous in operation on the Apache Railway.  Unfortunately, those in operation on short line Arkansas & Missouri (the fabled Alco line) have an uncertain future after the railroad announced in July it was acquiring three new SD70ACes and would retiring much of its Alco fleet.   

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