# EMD E and F units
EMD E and F units were two families of cab-unit diesel locomotives built by Electro-Motive (EMC, later EMD) in a shared streamlined "covered wagon" carbody: the E series of 1937–1963 for passenger service and the F series of 1939–1960 for freight and general service.
| Key fact | Detail |
|---|---|
| Name origins | "E" stood for eighteen hundred horsepower, the E series' installed power; "F" stood for Freight [1](https://www.american-rails.com/cab.html) • [2](https://www.loco-info.com/view.aspx?id=13845&t=) |
| Production spans | E units May 1937 to December 1963; F units 1939 to 1960 [3](https://www.trains-and-railroads.com/emd-e-units) • [2](https://www.loco-info.com/view.aspx?id=13845&t=) |
| F-series total | More than 7,500 F units built [2](https://www.loco-info.com/view.aspx?id=13845&t=) |
| Largest early FT buyer | Santa Fe, with 320 A and B units [4](https://www.american-rails.com/e390.html) |
| FT demonstration | Four-unit set, 20 Class I railroads, 83,764 miles, 35 states in eleven months [5](https://www.american-rails.com/e422.html) |
| Power | 16-cylinder EMD 567 prime mover; E8 2,250 hp; F9 1,750 hp with the 567C [2](https://www.loco-info.com/view.aspx?id=13845&t=) • [3](https://www.trains-and-railroads.com/emd-e-units) |
| Survivors | Several units remain operable on tourist lines and in museums; Union Pacific keeps E9s for its business train [1](https://www.american-rails.com/cab.html) |
## What E and F units were
Electro-Motive introduced the cab-unit concept publicly in 1937, when the Baltimore & Ohio's EA began powering the Capitol Limited. The "E" in the designation stood for eighteen hundred horsepower, and "A" described it as a cabbed unit. These were locomotives of EMC's own standardized in-house design, expandable to meet various power requirements; economies of scale made diesel power a full-sized replacement for steam in passenger service. The E1 of 1937–1938 comprised 8 A units and 3 B units [3](https://www.trains-and-railroads.com/emd-e-units).
The freight counterpart arrived in 1939 as the FT, where "F" stood for Freight (the source renders "T" as Twenty-seven hundred horsepower). It wore a more rounded nose than the E units, nicknamed the "Bulldog" [1](https://www.american-rails.com/cab.html). That bulldog nose became a signature carried by all later EMD cab models [5](https://www.american-rails.com/e422.html).
## How the design worked
F units drew power from the 16-cylinder variant of EMD's 567-series prime mover [2](https://www.loco-info.com/view.aspx?id=13845&t=). The F9, the last F-series model, produced 1,750 hp using the 567C engine [2](https://www.loco-info.com/view.aspx?id=13845&t=). On the passenger side, the E7 delivered 2,000 hp with the 567A engine and the E8 2,250 hp with the 567B [3](https://www.trains-and-railroads.com/emd-e-units). The sources document the starting and ending power levels of the F series but not each intermediate step.
The carbody itself served several purposes beyond hiding the machinery. According to the FT history, the reasoning was multifaceted: redundancy inherited from the streamlined E units, advertising for GM's new product line, and safety, because the frame was designed to fracture behind the cab in a collision, giving the crew a measure of protection [5](https://www.american-rails.com/e422.html).
A practical consequence of the design was that F units normally ran in multiple-unit sets, with cabless B units matched to cabbed A units; the FT's 555 A and 541 B units were built as matching pairs [1](https://www.american-rails.com/cab.html). The sources state the B-unit matching but do not give the underlying technical reason single-unit operation was impractical, so that explanation is left open here.
## By the numbers
F-series production is well documented at the extremes. By the end of FT production in 1945, EMD had built 555 A units and 541 B units [1](https://www.american-rails.com/cab.html). Across the whole series, more than 7,500 F units were built between 1939 and 1960 [2](https://www.loco-info.com/view.aspx?id=13845&t=).
Mid-series totals are reported differently even within the same specialist publisher. One source credits the F3 with more than 1,800 A and B units over its four-year run and the F7, built 1949–1953, with 3,849 combined units, more than any other F model [1](https://www.american-rails.com/cab.html). A second source gives roughly 1,111 F3s, 2,366 F7s, and 87 F9 A units [4](https://www.american-rails.com/e390.html). For the F9, the technical database gives 101 A units and 156 B units sold [2](https://www.loco-info.com/view.aspx?id=13845&t=).
E-series output: the E7 (1945–1949) totaled 428 A units and 82 B units, and the E8 (1949–1954) totaled 450 A units and 46 B units [3](https://www.trains-and-railroads.com/emd-e-units). Santa Fe was the first and largest early FT customer, ordering 320 A and B units on its own [4](https://www.american-rails.com/e390.html).
## Role in ending steam
The turning point was the FT demonstration. A four-unit demonstrator set toured for eleven months, operating on 20 Class I railroads and covering 83,764 miles in 35 states. In the process it convinced the industry of diesels' superiority in main line service [1](https://www.american-rails.com/cab.html) • [5](https://www.american-rails.com/e422.html).
The demonstration did not introduce the diesel locomotive itself; boxcabs, switchers, and passenger units had already proved the technology. What the F-unit boom confirmed was that diesel-electrics were ready for the hardest freight assignments [5](https://www.american-rails.com/e422.html). Sales followed quickly: before 1950, EMC/EMD had sold over 1,000 FT units, making the company the industry leader in diesel locomotives and setting a standard other manufacturers followed [4](https://www.american-rails.com/e390.html). The FT's 555 A and 541 B units are credited with spelling doom for mainline steam [1](https://www.american-rails.com/cab.html).
## How they compare with rivals
Every major competitor fielded a covered-wagon response. [Fairbanks Morse](https://www.edgepedia.org/fairbanks-morse) debuted the Erie Built in 1945, Alco introduced the PA and FA models in 1946, and Baldwin's DR-4-4-1500 of 1947 carried a "Baby Face" carbody later restyled into [Raymond Loewy](https://www.edgepedia.org/raymond-loewy)'s "Sharknose" [1](https://www.american-rails.com/cab.html).
None of these matched EMD's results. Aside from Alco's somewhat successful PA/FA models, no other builder really competed against EMD's covered wagons, which combined reliability with a look no rival could match [1](https://www.american-rails.com/cab.html). The evidence available here does not quantify reliability differences or market-share percentages beyond these production totals.
## References
1. Cab Units (Locomotives): Types, History, Manufacturers — https://www.american-rails.com/cab.html
2. Electro-Motive Company F series — https://www.loco-info.com/view.aspx?id=13845&t=
3. EMD E Units | Trains and Railroads — https://www.trains-and-railroads.com/emd-e-units
4. EMD "F" Units (Locomotives): Specs, History, Photos — https://www.american-rails.com/e390.html
5. EMD "FT" Locomotives: Specs, Roster, History — https://www.american-rails.com/e422.html
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*Topic: Encyclopedia › Technology and the built world › Transport and spaceflight › Rail transport › Rail vehicles and rolling stock › Diesel, electric, and wartime locomotives › North American diesel and electric locomotives › EMD E and F unit passenger/cab locomotives*
*Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026 · Edited: Oct 11, 2026 · Last review: Sep 30, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license