Diesel Locomotives: History, Models, And Manufacturers

Published: December 5, 2021

Diesel locomotives, technically known as diesel-electrics, came into widespread use following development of Electro-Motive Corporation’s (later, General Motors' Electro-Motive Division) EA/EB design, first tested on the Baltimore & Ohio Railroad (B&O) in 1937.  

The motive power's genesis, however, dates back even further to the World War I period when an early switcher model entered service.  

The industry remained skeptical of the diesel for many years, relegating it to secondary status while steam remained the preferred choice for main line assignments.   

This changed after General Motors successfully demonstrated the diesel's viability during testing of its FT freight design in 1939.   

The demonstrator set toured the country, convincing skeptic after skeptic that diesels were not only efficient and reliable but could also outperform the iron horse. 

Today's newest models offer even great advancement, heavily computerized to monitor almost every aspect of a locomotive while in service.  

As a result, the "old school" ways in which an engineer operated theirs has been taken away through technological improvements in models like the SD70ACe-T4 and ES44AC.

A diesel-electric's mechanics are rather straightforward although it is commonly mistaken that the diesel engine propels the locomotive.  This is not the case.  

Santa Fe F7A #261-C (an early variant sporting the chicken wire grill) and other Fs lead their freight south out of Denver near Castle Rock, Colorado on April 15, 1965. American-Rails.com collection.

How A Diesel Locomotive Works

While the engine is the prime mover the energy it creates drives an electric generator, which in turn powers the traction motors found within the locomotive’s trucks.  The latter are responsible for turning the wheels and propelling the unit forward. The engine, itself, has no connection to the actual motion.  

In essence, the diesel is an electric locomotive with its own power plant.  What is the difference?  A true electric is provided power via electricity through either overhead catenary or third-rail while a diesel-electric carries its own (engine) on board.  

A History Of The Diesel Locomotive

This motive power type has been around in one shape or form since 1904-1905 when Southern Pacific took delivery of an early test-bed design according to Brian Solomon's book, "GE Locomotives." 

General Electric was directly involved in this project by supplying the locomotive's generator and electric equipment. 

In 1917, GE was back at it when the company began testing an experimental model utilizing a GM-50 prime mover (a V-8 diesel engine designed by GE).  

A year later it launched formal production of these 225 horsepower machines; the line was largely considered a failure although a few were sold; one to the Jay Street Connecting Railroad (#4), another to the city of Baltimore and finally one to the U.S. Army.

Undeterred by this experiment's lackluster performance the company pressed forward with a new design in 1923.  

This latest trial carried GE electrical components, a prime mover from Ingersoll-Rand (capable of 300 horsepower), and a carbody provided through American Locomotive (Alco).  

As the late historian Jim Boyd notes in his book, "The American Freight Train," the 60-ton boxcab was finished in 1924 and proved a success.

 It eventually sold to the Central Railroad of New Jersey (#1000) where it spent many years in switching assignments around New York City.  

Ironically, despite the company's pioneering ways it never launched its own formal locomotive line until the late 1950's.  

It did remain involved, however, by partnering with Alco providing it components (such as traction motors) while also pioneering early electrification systems and locomotives.

 In time, the Schenectady builder continued to lose market share against Electro-Motive, spurring GE to launch its own "Universal" line in 1959.  

While a commercial success the series was not particularly reliable (many of these so-called "U-boats" had a lifespan of only a few decades).

Once more, GE did not give in and spent many years fine-tuning its design until it had overtaken EMD by the 1980's.

Santa Fe F7A #335-L eases out of the siding with a southbound freight at Ardmore, Oklahoma as the train crosses 5th Avenue on February 27, 1974. American-Rails.com collection.

The early boxcabs are often credited as the first with a diesel engine although the very first railcar to utilize an internal combustion engine was the McKeen Car.

In Brian Solomon's book, "The American Diesel Locomotive," the idea for this concept came from William McKeen, Union Pacific's chief of motive power.  

Even by the early 20th century railroads were attempting to cut costs on lightly patronized branch lines and UP's leader, the legendary Edward Harriman, approached McKeen in 1904 about developing a self-powered railcar for use on these secondary corridors.  

After many tests at the Electric Railway Test Commission in St. Louis they came up with an aerodynamic design powered by a 100 horsepower, gasoline engine manufactured by early pioneer, Riotte.

The first unit, listed as #M-1 and given the name "Windsplitter," was completed at UP's shops in Omaha, Nebraska during March of 1905.  

Following a refinement which featured a longer frame and marine engine (producing twice the horsepower), Harriman was impressed.  He allowed McKeen to setup production of the McKeen Railcar Company in 1908.

Early on McKeen was successful but soon ran into reliability issues and sales had flattened by 1912. While the "Windsplitter" had its issues other companies were triumphant (including GE and Electro-Motive) in producing a reliable railcar for branch line service, the so-called "Doodlebug."  

Their achievements eventually led to the diesel-powered boxcab switchers mentioned above.  These early examples proved their worth in branch line and secondary assignments.  

The transition from steam to diesel was a fascinating era in American railroading. Here, Baltimore & Ohio E7A #66 (about a year old) and 4-6-2 #5086 (Class P-1a) await their next assignments in Cumberland, Maryland during October, 1946.

However, usurping steam's dominance in main line service was another matter entirely.  The venerable Baltimore & Ohio was always a technological trailblazer and with the diesel it was no different.  

It holds the distinction as the first to utilize one for main line service, Electro-Motive's boxcab #50, manufactured in 1935. 

Delaware & Hudson PA-1 #18 pours on the smoke as the Alco departs Mohawk Yard near Alplaus, New York with the northbound "Laurentian" during the late 1960s. Jim Shaughnessy photo. American-Rails.com collection.

Electro-Motive took this boxcab and upgraded its prime mover with a rugged General Motors model 567 while shrouding it within a sleek carbody.  

This FT demonstrator A-B-B-A set, #103, began testing across the country in November of 1939.  As Brian Solomon notes in his book, "Electro-Motive E Units And F Units," it proved itself time again, such as on Southern Pacific's Tehachapi Grade where it outperformed SP and Santa Fe steamers (the AT&SF held trackage rights in this territory). 

According to David Morgan's article, "The Diesel That Did It," from the February, 1960 issue of Trains Magazine during their trials the locomotives traveled 83,764 miles on twenty Class I's in thirty-five states over an eleven-month period.  

Many, like the Santa Fe and Southern Pacific, were so impressed they immediately placed orders.  Others, like New York, Ontario & Western purchased the model based on word-of-mouth.  

It would take the diesel nearly fifty years to equal the horsepower output of a single steam locomotive during its technological height.

An aging Norfolk & Western RS-11, another one of which is showing its Nickel Plate heritage, has rescued a Conrail freight, led by ex-Penn Central F7's, on July 27, 1976. The train stalled on the grades over the former Erie Lackawanna's Niagara Falls Branch, bound for the Black Rock Branch in Buffalo, New York. Doug Kroll photo.

However, diesels made up for this disadvantage in other ways. They required far less maintenance, including heavy overhauls, and could operate much further between refueling stops.  

This meant diesels could spend more time on the road doing what they were designed for, paying the bills.  In addition, thanks to MU (Multiple Unit) technology a single engineer from the lead locomotive could control several trailing units, increasing the horsepower output per train.  

As Mr. Solomon notes, while American Locomotive, General Electric, and Ingersoll-Rand spearheaded the diesel's development, it was General Motors/Electro-Motive which successfully mass-produced them for main line service.  

GM had already entered the auto industry and recognized that durable internal mechanics coupled with a rugged prime mover (the model 567) could mean big business.  This led to cab designs packaged within an attractive carbody and the rest, as they say, is history.

Southern Pacific H24-66 "Train Master" #3025 is ahead of commuter train #131 as it nears San Francisco's South City Station, circa May, 1969. Drew Jacksich photo.

Electro-Motive (EMD): Production Totals, Photos, Specifications & More

A History of General Motors' Electro-Motive Division (EMD)

EMD's Canadian Division, General Motors Diesel

Early EMC Switchers: SW, SC, NW, NC 

"Cow-Calf" Switcher Designs








SW1001 Variant



MP15DC/AC/T Series

EMD's E Series 



Seaboard Air Line's E4

Burlington's E5


Rock Island's Unique AB6




EMD's F Series 







New Haven's FL9

F40PH Series

F45 Series

SDP40F Passenger Variant


Great Northern's GP5



GP15 Series






GP38 Series

GP40 Series



EMD/Alco MRS-1


SD9, "Cadillac"




SD38 Series

SD40/SD40-2 Series

SD45 Series


SD60 Series

SD70 Series





Odd/Unique Designs

B Units

C&NW's Crandall Cabs


DDA40X, "Centennial"

Draper Taper

Krauss-Maffei ML-4000



Tunnel Motors

Wabtec Freight (Formerly GE Transportation)

Wabtec Freight

Notable Prime Movers

Alco's Model 244

Alco's Model 251

EMD's Model 567

EMD's Model 645

EMD's Model 710

Truck Types

AAR Type A/B

Blomberg Type A/M



Related Companies/Designs

Davenport Locomotive Works

Plymouth Locomotive Works

Other Reading


Gensets/Green Goats

Rail Diesel Car, RDCs


Notable Events/Programs

Norfolk Southern's Heritage Program

Streamliners At Spencer

Union Pacific's Commemorative Series

Common Designs


Cab Unit


Transfer Switcher

"Pushing the limits of the camera and photographer. Thanks to a sudden heavy rainfall, the progress of CSX H802 with 37 loads of coal from Rainelle, West Virginia nosedived when they hit the 3.5 mile long 1.7 percent uncompensated grade between Bellwood and Spring Dale on the former Nicholas, Fayette & Greenbrier line (uncompensated means the curvature is not factored into the grade, and with curves up to 20 degrees, the grade is actually over 2 percent for most of the hill, including this location). With daylight nearly gone, and after listening to the train coming for nearly 20 minutes, we finally get a change to click the shutter. The result was much more impressive than if the train been here earlier. So here's H802 coming upgrade at 3 miles per hour, and I'm shooting wet, cold, and handheld at a 400mm composition at 1/100th, f5.6, iso 10,000 with the 6d and 150-600 Tamron." - Loyd Lowry

Diesels have come a long way from the EMC and Alco-GE-IR boxcabs of the 1920's.  Today's models, manufactured by Wabtec Freight (successor to General Electric) and Progress Rail (successor to EMD), are equipped with comfort cabs, air conditioning, and advanced electronics. During the early days there were more than just two builders.  

After Electro-Motive opened a new motive power market many joined in, including Alco, Lima, Baldwin, Fairbanks-Morse, and later GE.  The former had been the longstanding "Big Three" steam manufacturers.  

They had produced thousands of high-quality locomotives during their heyday but unfortunately could never make the successful transition to diesel technology.  

Alco was the last holdout, finally closing in 1969.  Fairbanks-Morse was a bit of an outlier with a history tracing back to the 19th century.  

It became a leader of the opposed-piston marine engine and decided to enter the diesel market during the 1940's.  

Unfortunately, it couldn't establish a foothold after a decade and gave up (but is still in business today).  EMD never, truly recovered after losing its top spot in the 1980's, which led to its sale by General Motors in 2005.  

Today, the corporate division has been dissolved altogether and Progress Rail only uses the company name for marketing purposes.  A testament to its first and second-generation models endures, however, as those built more than a half-century ago can still be found in revenue service today!

  1. Home
  2.  ›
  3. Diesel Locomotives


Wes Barris's SteamLocomotive.com is simply the best web resource on the study of steam locomotives. 

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

It is quite staggering and a must visit!