Milwaukee Road Boxcab Electrics (EP-1 / EF-1): History, Specs & Classes

Last revised: September 1, 2026

The Milwaukee Road’s boxcabs were the first motors on the 3,000-volt DC Pacific Extension. Alco built the carbodies and running gear; General Electric built the electrical equipment. Forty-two locomotives—84 half-units, each pair numbered as one engine with A and B ends—came west in 1915–16. Thirty pairs were freight EF-1s (10200–10229). Twelve were passenger EP-1s (10100–10111), higher geared, with oil-fired train-heat boilers. They opened the railroad under catenary on November 30, 1915, worked both electrified divisions, and a Harlowton switcher pair was still under the wire when the system died in June 1974. Two pieces survive: pair E50 (the original 10200) at the Lake Superior Railroad Museum in Duluth, and switcher half-unit E57B at Harlowton, Montana.

Milwaukee Road boxcabs led by E-34B about to couple onto a train at Butte Montana circa 1965

Milwaukee Road boxcabs, led by E-34B, about to couple onto their train at Butte, Montana, circa 1965. American-Rails.com collection.

On this page: At a glance · Two divisions under 3,000 volts · 10200 and “King of the Rails” · How a pair was built · Specifications · EP-1 and EF-1 as built · EF-2, bobtails, EF-5, ES-3 · Mountain and Coast · The 1950s passenger rebuilds · June 1974 · Class tables · E50 and E57B

At a Glance

Item	Detail
Railroad	Chicago, Milwaukee & St. Paul; later Chicago, Milwaukee, St. Paul & Pacific (Milwaukee Road)
Builders	American Locomotive Company (mechanical) and General Electric (electrical)
Built	1915–16 (last half-units into early 1917)
Quantity	42 locomotives / 84 half-units. 30 freight pairs, 12 passenger pairs
As-built classes	EF-1 freight 10200–10229; EP-1 passenger 10100–10111
Wheel arrangement (pair)	AAR 2-B+B+B+B-2; UIC (2′Bo)(Bo)+(Bo)(Bo2′). Each half-unit is 2-B+B
Wire	3,000 V DC overhead (later some substations toward 3,400 V)
Horsepower (pair)	4,100 1-hour / 3,340 continuous (this site’s long-standing sheet). Period GE-253-A math: 3,440 / 3,000
As-built speed	Freight about 35 mph; passenger geared near 60 mph
Later speed	Freight re-geared to 45 mph in the 1950s rebuilds
Territory	Rocky Mountain Division (Harlowton, Mont.–Avery, Idaho) and Coast Division (Othello–Tacoma/Seattle). Avery–Othello was never wired
In service	First train November 30, 1915; last regular use June 1974
Later classes from the same fleet	EF-2 (three half-units), EF-3 (bobtail middle), EF-5 (four half-units), ES-3 (surplus half as switcher), EP-1A (1950s passenger rebuilds)
Survivors	E50A+B (née 10200A+B), Lake Superior Railroad Museum, Duluth, Minn. E57B (née 10211B), static at Harlowton, Mont.

Two divisions under 3,000 volts

Milwaukee electrified the Pacific Extension in two pieces, both 3,000-volt DC, with a long steam (later diesel) gap between them - a gap the railroad intended to close but ultimately never did. The Rocky Mountain Division, Harlowton to Avery, is about 438–440 miles. Feasibility work with GE started in 1913. Wire went up in 1915–16; the mountain was in full electric operation by 1917. The first revenue electric move was November 30, 1915, Butte to the east side of Pipestone Pass—over Vendome Loop on the 2 percent east slope. The Coast Division, Othello to Tacoma and Seattle, about 208–216 miles, was completed in 1920. Snoqualmie Pass tunnel had construction power earlier. Together the two islands were on the order of 656 route miles. Avery to Othello was never under catenary.

A separate GE steeple-cab, class ES-1 number 10000, went to work in the Great Falls, Montana, yard in the summer of 1915 on 1,500 volts. That is not this class. The boxcabs are the main-line 3,000-volt motors.

Michael Sol, on an engineering inspection of the electrified plant in the 1970s, found the locomotives and much of the fixed plant still serviceable. The trolley and the ties were the worn-out parts. The railroad shut the wire down anyway. The oil shock that followed is a system story this site has told before.

Milwaukee Road boxcab set E-45 at Deer Lodge Montana February 2 1962 C G Heimerdinger Jr

Milwaukee Road boxcab set E-45 at work in Deer Lodge, Montana, February 2, 1962. C.G. Heimerdinger, Jr. photo.

10200, “King of the Rails,” November 30, 1915

GE and Alco billed the first pair, 10200A+B, as the largest electric locomotive in the world. It was displayed at Butte in October 1915. Delivery is dated September 25, 1915. On November 30 it took the first electric train east from Butte up Pipestone. GE’s 1915 silent promotional film called the design “King of the Rails.” Period claims also called it the first high-voltage DC road locomotive and the first with regenerative braking; treat those as 1915 publicity, not a worldwide patent search. The motors themselves followed GE practice already running on the Butte, Anaconda & Pacific, the Detroit River Tunnel, and the Baltimore & Ohio, at a higher trolley voltage.

The demonstration that sold the board was a grade test east of Butte on the 1.66 percent west slope of Pipestone. A 3,000-ton train with a two-unit boxcab on the point and a second pair as helper held 16 mph. A 2,000-ton steam freight with two 2-8-2s on the head end and a 2-6-6-2 helper made 9 mph on the same hill. That is the comparison the railroad used. It is not a claim that every later freight ran 3,000 tons at 16 mph.

Two half-units, not an A-A diesel set

Each locomotive is two boxcab half-units, semi-permanently coupled back-to-back, numbered as one engine with A and B suffixes. Crews and shopmen called the halves motors. They are not diesel-style A units running as an A-A set. The AAR arrangement of a complete pair is 2-B+B+B+B-2: an unpowered two-axle guiding truck at each outer end and four two-axle powered B trucks between. UIC is (2′Bo)(Bo)+(Bo)(Bo2′).

The two powered trucks on a half-unit are joined with a ball-and-socket while the couplers ride on the trucks. The carbody does not take the draft of the train. Outside bar frames left room for axle-hung motors. The front powered-truck frames extend forward as an outrigger for the idle truck and the heavy snowplow each outer end carried.

Each pair had eight Type GE-253-A motors, 1,500-volt machines insulated for 3,000 volts to ground, twin-geared to the driving axles—a pinion on each end of the armature shaft. Armstrong’s 1915 paper and the 1916 Electrical Age sheet rate one motor 430 hp for one hour and 375 hp continuous, so eight motors are 3,440 / 3,000 hp. Later Milwaukee and secondary sheets quote 4,100 hp one-hour and 3,340 continuous for the pair; some of that spread is input-to-motors versus output.

Multiple-unit control was on the locomotives straight from the factory and two pairs could be handled by the engineer from one cab. That is ordinary 1915 MU, the same idea already in suburban multiple-unit cars. Milwaukee later added its own MU so a boxcab could lead trailing diesel-electrics; the Little Joes got a similar hookup and used it more often. Regenerative braking put power back in the trolley on the downgrade. That, not MU, was the feature the 1915 publicity leaned on.

Milwaukee Road boxcab set E49 between assignments at Deer Lodge, Montana, August 14, 1967. American-Rails.com collection.

Specifications (as-built pair)

Figures below are one complete two-unit locomotive, classes EF-1 / EP-1 as delivered. Rebuild classes change length, weight, and horsepower; those are in the class table farther down. Period 1915–16 sheets and the later 4,100 / 3,340 rating are both shown rather than picking a winner.

Specification	Value
Builders	Alco (mechanical), General Electric (electrical)
Years built	1915–16; last documented half-units early 1917
Wheel arrangement (pair)	2-B+B+B+B-2 (AAR); (2′Bo)(Bo)+(Bo)(Bo2′) (UIC); 4-4-4-0+0-4-4-4 OE Whyte
Half-unit arrangement	2-B+B
Gauge	4 ft 8½ in standard
Electrical system	3,000 V DC overhead, pantographs
Traction motors	Eight GE-253-A, axle-hung, twin-geared (four per half-unit)
Motor rating (each)	430 hp 1-hour / 375 hp continuous (1915–16 GE sheet)
Locomotive 1-hour rating	3,440 hp (eight motors). Later sheets 4,100 hp
Locomotive continuous rating	3,000 hp (eight motors). Later sheets 3,340 hp
Starting tractive effort	About 103,000 lbf on later sheets; 1915 Armstrong paper about 120,000 lbf at 30% adhesion
Continuous tractive effort	71,000 lbf (1916 Electrical Age)
Gear ratio, freight	4.56
Gear ratio, passenger	2.45 (71:29 on the 1950 passenger rebuild sheet; same ratio as built)
As-built maximum speed	Freight about 35 mph (armature limit). Passenger geared near 60 mph
1950s freight re-gear	45 mph
Driving-wheel diameter	52 in
Guiding-wheel diameter	36 in
Length over couplers	112 ft (Railway Age Gazette, Oct. 15, 1915; 1916 sheets). 1950 passenger rebuild sheet 112 ft 6 in
Total wheelbase	102 ft 8 in
Rigid wheelbase	10 ft 6 in (1916 sheet); some later tables 10 ft
Width	10 ft 0 in (1950 rebuild sheet)
Height	15 ft 0 in (1950 rebuild sheet, pans excepted)
Total weight	564,000 lb
Weight on drivers	448,000 lb
Weight per driving axle	56,000 lb
Weight per guiding axle	29,000 lb
Passenger extras as built	Oil-fired steam boilers, one in each half-unit, about 4,000 lb/hr evaporation for the pair; passenger gearing

Milwaukee Road boxcab set E29 between assignments in Butte, Montana, August 1965. American-Rails.com collection.

Thirty freight pairs, twelve passenger pairs

The order was 42 locomotives. Freight EF-1s 10200–10229 were geared for 35 mph and the 2 percent mountain. Passenger EP-1s 10100–10111 took the Olympian and other varnish on the new wire with 2.45 gearing and steam heat. GE’s 1915 passenger rating was an 800-ton train at about 60 mph. The two classes were the same machine except for gears and boilers.

In 1919, with the EP-2 Bipolars and EP-3 Quills arriving for passenger work, Milwaukee converted the twelve EP-1s to freight: boilers off, freight gearing, numbers 10230–10241 as EF-1s. After that the original 42 pairs were all freight motors until the 1930s combinations and the much later EP-1A rebuilds.

First unit 10200A+B is GE serials 5022A and 5022B, Alco/GE, September 1915. It kept its identity as E50A+B after the 1939 renumbering and is the pair in Duluth. Interestingly, throughout their service lives the hal-unit sets were swapped among consists without the road number following the carbody; some motors wore two, three, even seven numbers before they were cut up.

EF-2, bobtails, four-unit EF-5s, and the leftover switcher

Train tonnage grew. In the 1930s Milwaukee started making three-unit locomotives out of boxcab halves. A straight three-unit set is class EF-2. Twelve were assembled and numbered 10500–10511, A-C-B. The middle (C) cab was dead weight. Shops cut those center units down: cab off, pilot truck off, frame extension off. Shopmen called them bobtails. A bobtail between two standard halves is class EF-3, about 52,000 lb lighter than an EF-2 with a full middle unit (23.6 metric tons in the German-language summary; 51,000 lb on some English sheets). Later EF-2s were made without repeating the bobtail cut. Diesel Shop notes twelve halves shortened about 14 feet; listed examples include E25C/D, E30C/D, E33C, E34C/D, E35C, and E52C, plus three others.

In 1939 Milwaukee renumbered the electric fleet into the E-series. EF-3s became E25–E36. Remaining two-unit EF-1s became E50–E73. Those blocks did not stay tidy. Four-unit EF-5 consists appeared in 1951 (five of them) and grew to ten by 1961. Any mix of standard and bobtail halves could sit in the two middle positions. An EF-5 could stretch about 224 feet and weigh about 1,128,000 lb. One-hour output on a four-motor-group set is about 8,200 hp; continuous about 6,680.

Assembling three-unit sets left an odd half-unit. Milwaukee classed it as a heavy switcher, ES-3. That motor is E57B, originally 10211B, GE 5110B, February 1916. It became the Harlowton switcher, often with a bobtail companion, and it is the other survivor.

Milwaukee Road boxcab set E-30 eastbound freight at Othello Washington circa 1962

Milwaukee Road boxcab set E-30 with an eastbound freight at Othello, Washington, circa 1962. Othello is Coast Division. American-Rails.com collection.

Rocky Mountain Division and the Coast

The boxcabs were road power on both wired islands. Joes never were. Coast substations were not rebuilt for the 1948–49 GE 2-D+D-2s, so Little Joes stayed on the Harlowton–Avery section. Boxcabs kept Coast freight—Othello, Beverly, the Columbia River crossing—and they kept helper and local work on the mountain after the Joes took the time freights. The live photographs on this page are the evidence: E-30 at Othello about 1962, E32B at Beverly on December 31, 1958, E-37 as an EF-5 near Alberton in 1954, E47B at Three Forks in 1968.

As built they were not fast. Freight gearing stopped at about 35 mph because the armatures would not take more. The railroad lived with that for a generation. In the 1950s rebuild program the freight motors were re-geared for 45 mph. By then the Joes were already on the mountain. The rebuild was about keeping schedules with the old fleet, not about making the boxcabs into Joes.

Milwaukee Road boxcab E49-A at Deer Lodge, Montana, in 1968. American-Rails.com collection.

EP-1A: passenger motors on freight frames, 1950–61

Do not confuse the 1915 EP-1s with the 1950s passenger rebuilds. The originals had already been freight motors for thirty years. In 1950 Milwaukee issued a Class EP-1 general description (on Sol’s site) for a geared passenger locomotive constructed on the frame of a Class EF-1 freight locomotive: 71:29 gears, 8-EL brakes in place of 14-EL, steam generators added. Weight on that sheet is 650,000 lb total, 500,000 on drivers; starting effort 150,000 lbf at 25% adhesion. Output after the rebuild is quoted at 4,500 hp.

Two pairs were treated. English-language summaries date the outshopping to 1953: E69A/B became E22A/B first (photographed after overhaul February 26, 1953, on Sol’s site); E28A/B followed as E23A/B. They received steam generators, engine trucks from scrapped F7 Hudsons, and high-speed gearing. E22A got a smoothed, somewhat streamlined cab front. They later wore the Union Pacific–inspired Armour Yellow with Harbor Mist Gray roofs that Milwaukee put on some passenger motors. They helped the aging Bipolars on the Coast. After the Olympian Hiawatha died in May 1961 they went back to freight. E23A/B were renumbered E22D/C and the four halves ran as EF-5 E22. E22C was wrecked in 1966; A/B/D lasted until 1973.

Milwaukee Road boxcab set E45 with E45B closest layover at Harlowton Montana August 1967

Milwaukee Road boxcab set E45, E45B closest to the photographer, layover near the roundhouse at Harlowton, Montana, August 1967. Photographer unknown. American-Rails.com collection.

Worn out, patched, then June 1974

The fleet stayed intact until 1951, when EF-1s E51A+B and E68A+B were retired. Two units of an EF-2 went in 1954. The rest held into the mid-1960s, then old age. Shops patched motors until they could not, and swapped halves between locomotives without renumbering. Most were out by the end of 1973. One combination remained: E57B and a bobtail companion as the Harlowton, Montana, switcher, still working in June 1974 when the Rocky Mountain electrification was shut down. The Joes took the last road freight on June 15. The boxcabs took the last yard job.

What followed is familiar to anyone who knows Lines West. The railroad had paid for the motors and the substations decades earlier. It then bought diesel fuel and diesel locomotives to replace them, just as oil prices rose. That decision is not a locomotive-spec problem. The boxcabs had already outlived every reasonable replacement cycle.

Milwaukee Road boxcab E49B, and mates, at the yard in Butte, Montana, circa 1959. Photographer unknown. American-Rails.com collection.

Class tables

As built, 1915–16

Class	Road numbers	Pairs	Role	Notes
EF-1	10200–10229	30	Freight	35 mph gearing. 10200A+B delivered Sept. 25, 1915; first train Nov. 30, 1915
EP-1	10100–10111	12	Passenger	2.45 gearing, oil-fired boilers. Converted to EF-1 10230–10241 in 1919

Horsepower for either class as a pair: 4,100 1-hour / 3,340 continuous on this site’s long-standing sheet; 3,440 / 3,000 from the GE-253-A motor ratings.

Rebuild classes from the same 84 half-units

	EF-1 (pair)	EF-2 (3 halves)	EF-3 (3 halves, bobtail middle)	EF-5 (4 halves)
When	1915–16 as built	1930s; twelve numbered 10500–10511 ACB	1930s, from EF-2 middles cut down	1951 (five), ten by 1961
Wheel arrangement	2-B+B+B+B-2	2-B+B+2-B+B+B+B-2	2-B+B+B+B+B+B-2	2-B+B+2-B+B+B+B-2+B+B-2 (center two may be bobtails)
Length	112 ft	168 ft	shorter than EF-2 by the bobtail cut (~14 ft off the middle)	about 224 ft
Service weight	564,000 lb	845,000 lb	794,000 lb (~52,000 lb lighter than EF-2)	1,128,000 lb
1-hour hp	4,100 (3,440 on 1915 motors)	6,150	same order as EF-2 (three motor groups)	8,200
Continuous hp	3,340 (3,000 on 1915 motors)	5,010	same order as EF-2	6,680
Starting TE	103,000 lbf	154,500 lbf	—	205,700 lbf
1939 numbers	E50–E73 (remaining pairs)	—	E25–E36	various E-series consists (E22, E25–E49 range in later years)

ES-3: leftover half-unit used as a heavy switcher. E57B, née 10211B. Harlowton. Preserved there.

EP-1A: two pairs rebuilt for passenger, 1950 description / 1953 outshop. E22A/B and E23A/B (later E22D/C). Steam generators, F7 engine trucks, 71:29 gears, 4,500 hp quoted, E22A streamlined. Passenger to March 1961; freight as EF-5 E22 afterward.

Milwaukee Road boxcab set E-37 EF-5 near Alberton Montana June 10 1954

Milwaukee Road boxcab set E-37, class EF-5, near Alberton, Montana, June 10, 1954. Photographer unknown. American-Rails.com collection.

Milwaukee Road boxcab E47B westbound freight arriving Three Forks Montana June 8 1968

Milwaukee Road boxcab E47B arrives in Three Forks, Montana, with a westbound freight, June 8, 1968. American-Rails.com collection.

Two survivors

E50A+B, originally 10200A+B, is the first locomotive built. Milwaukee donated the pair to the Lake Superior Railroad Museum in Duluth in 1977. It sits as Milwaukee Road 10200. The museum has at times allowed visitors into the cab. Confirm current access before you plan a trip around that. American-Rails.com does not operate the exhibit.

E57B, originally 10211B, class ES-3, is on static display at Harlowton, Montana—the east end of the Rocky Mountain wire, where it switched until the last month. The older copy of this page mentioned only E50. E57B is the other half of the story, and the live photo of it at Harlowton about 1970 was already on the page.

Everything else was scrapped. There is no operating Milwaukee boxcab.

Milwaukee Road yard at Beverly Washington December 31 1958 boxcab E32B closest to photographer

Milwaukee Road’s small yard at Beverly, Washington, December 31, 1958. Closest to the photographer is boxcab E32B. Coast Division. Photographer unknown. American-Rails.com collection.

Milwaukee Road boxcab ES-3 E57B at Harlowton Montana circa 1970

Milwaukee Road boxcab E57B at Harlowton, Montana, circa 1970. This is the ES-3 switcher, originally 10211B, later preserved in town. Photographer unknown. American-Rails.com collection.

Sources

A.H. Armstrong, “The Electrification of the Puget Sound Lines of the Chicago, Milwaukee & St. Paul,” 1915 (Sol): GE-253-A, 3,440 / 3,000 hp, 120,000 lbf at 30% adhesion, passenger 60 mph / 800 tons
“Electrification of 440.5 Miles of the St. Paul,” Railway Age Gazette, October 15, 1915: 112 ft, 564,000 lb
“The C.M. & St. P. Electrification,” Electrical Age, July 1916 (Sol): 102 ft 8 in wheelbase, 10 ft 6 in rigid, 448,000 lb on drivers, 52-in / 36-in wheels, gear ratios 4.56 freight / 2.45 passenger, 71,000 lbf continuous TE
Milwaukee Road, Class EP-1 Locomotives General Description, 1950 (Sol): rebuild on EF-1 frames, 71:29, 650,000 / 500,000 lb, 150,000 lbf at 25% adhesion
Milwaukee Road photograph, E22 after overhaul, February 26, 1953 (Sol)
Noel T. Holley, The Milwaukee Electrics (Hundman, 1999)
Electrification by General Electric Co., CERA Bulletin 116 (1976)
The Diesel Shop, Milwaukee Road electric motors, André Kristopan compilation (original numbers, GE serials, bobtails, E57B = 10211B, E50 = 10200)
William D. Edson, “Milwaukee Road Locomotives,” Railroad History 136 (Spring 1977)
“For More Than Half a Century,” Milwaukee Road Magazine, July–August 1973 (Sol): 10200 first train Nov. 30, 1915; 23 of 84 halves still available at phase-out; 440 / 216 miles
Railfan & Railroad, “Milwaukee Electrics: Fifty Years Gone” (2024): Sept. 25, 1915 delivery; Pipestone grade test; Coast 1920
Karl R. Zimmermann, The Milwaukee Road Under Wire
Lake Superior Railroad Museum: 10200 donated 1977
Tom Murray, The Milwaukee Road (MBI, 2005)
Jim Scribbins, The Hiawatha Story (University of Minnesota, 2007) and Milwaukee Road Remembered (University of Minnesota, 2008)
Charles R. Wood and Dorothy M. Wood, Milwaukee Road West (Superior, 1972)
Michael Sol, Milwaukee Road Archives

E50 is a static exhibit at the Lake Superior Railroad Museum in Duluth. E57B is a static exhibit at Harlowton, Montana. Confirm hours and cab access before you plan a visit around either locomotive. American-Rails.com does not operate the exhibits.