Alco "C-420" Locomotives

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 new Seaboard Air Line C420 is seen here in Raleigh, North Carolina circa 1965. Warren Calloway photo.

C-420 History And Background

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.

The Piedmont & Northern's only pair of C420's are seen here at work in Spartanburg, South Carolina on July 5, 1966. Warren Calloway photo (colorized).

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.

Lehigh Valley C-420 #409, GP18 #302, and other power layover at the yard in Pittston, Pennsylvania on June 29, 1969. Roger Puta photo.

From a technical standpoint the Alco 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 dominating 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.

Monon C420 #507 leads a southbound manifest across the Penn Central (ex-New York Central) and Elgin, Joliet & Eastern at Dyer, Indiana on March 27, 1971. David Hawkins collection.

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.

Alco C420 Data Sheet

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

Alco C420 Production Roster

Owner Road Number(s) Quantity Date Built
Erie Mining600-60231965
Lehigh & Hudson River21-2991963-1966
Lehigh Valley404-415121964
Long Island Rail Road200-229301963-1968
Louisville & Nashville1300-1315161964-1966
Mississippi Export6311965
Nickel Plate Road57811964
Norfolk & Western413-42081964
Piedmont & Northern2000-200121965
Seaboard Air Line110-136271965
Secratario de Communicaciones Y Transportes7123-10, 7123-1121965
Tennessee Central400-40121966


  • 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.

Shiny new Monon C420's at Vernia, Indiana on August 22, 1966. David Hawkins 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 EMD SD70ACes and would retiring much of its Alco fleet.   

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Wes Barris's is simply the best web resource in the study of steam locomotives. 

The amount of information found there is quite staggering; historical backgrounds of wheel arrangements, types used by virtually every railroad, preserved and operational examples, and even those used in other countries (North America and beyond). 

It is difficult to truly articulate just how much material can be found at this website.  It is a must visit!

Researching Rights-Of-Way

A popular pastime for many is studying and/or exploring abandoned rights-of-way. 

Today, there are tens of thousands of miles scattered throughout the country.  Many were pulled up in the 1970's and 1980's although others were removed long before that. 

If you are researching active or abandoned corridors you might want to check out the United States Geological Survey's (USGS) Historical Topographic Map Explorer

It is an excellent resource with thousands of historic maps on file throughout the country.  Just type in a town or city and click on the timeline of maps at the bottom of the page!