Milwaukee Road Class A 4-4-2: Specs, Roster, History

Published: September 28, 2026

The Milwaukee Road’s Class A was four streamlined 4-4-2s, numbers 1–4, built by the American Locomotive Company at Schenectady from 1935 to 1937 for the Hiawatha. They were among the last Atlantics built in the United States, and the largest. Eighty-four-inch drivers, 19-by-28-inch cylinders, and a 300-pound boiler gave them 30,685 pounds of tractive effort. The railroad designed them to cruise above 100 miles an hour with a full-size train, and to be capable of two miles a minute.

Alco’s April 1935 card for the design is class 442 S 280, order S-1740. Numbers 1 and 2 are that order. Numbers 3 and 4 followed in 1936 and 1937 on later serials. All four were scrapped. None were preserved.

Milwaukee Road Class A 4-4-2 number 3 at a station stop in Milwaukee, Wisconsin, with the Hiawatha on September 17, 1939

One of the Milwaukee Road’s lightning fast Class A 4-4-2s, #3 (according to Jim Scribbins’ book, “The Hiawatha Story,” she was outshopped from Alco on May 21, 1936), is seen here during a quick station stop at the Everett Street Depot in Milwaukee, Wisconsin with the “Hiawatha” (Chicago–St. Paul/Minneapolis) on September 17, 1939. The Atlantic normally cruised at 100 mph and covered the entire 409 miles from Chicago to St. Paul in just 390 minutes (6½ hours). To maintain its blistering schedule the railroad allowed just 2 minutes in Milwaukee for watering and handling passengers before the train was again on its way. Richard Kindig photo.

On this page: At a glance · A 4-4-2 for 1935 · What Alco delivered · The four engines · 112.5 miles an hour · Two minutes in Milwaukee · Hudsons, then the torch

At a glance

Item	Detail
Railroad	Chicago, Milwaukee, St. Paul & Pacific. Class A. Road numbers 1–4
Whyte	4-4-2. The railroad also called the type a Milwaukee
Builder	American Locomotive Company, Schenectady. Alco class 442 S 280. Order S-1740 is the April 1935 card, covering 1 and 2
Built	1 and 2, May 1935. 3, outshopped May 21, 1936. 4, April 1937
Serials	68684, 68685, 68729, 68828
Drivers and cylinders	84 in drivers. Two cylinders, 19 × 28 in. Walschaerts gear. 10-inch piston valves. Main rods on the front driving axle
Boiler	300 psi, conventionally staybolted. Oil fuel
Tractive effort	30,685 lb. Factor of adhesion 4.70 on 144,300 lb on the drivers
Weight, as carded	Engine 280,000 lb. Tender, loaded, 247,000 lb. Engine and tender 527,000 lb
Weight, 1945 diagram	Tender 277,443 lb, with oil raised to 5,544 gallons. Engine and tender 563,443 lb. The engine then weighs out at 286,000 lb
Tender, as built	13,000 gallons of water. 4,000 gallons of oil. Roller bearings on the engine and tender axles
Service	Hiawatha from May 29, 1935. Later the Morning and Afternoon Hiawathas, then the Midwest Hiawatha and secondary passenger trains
Retired	3 in September 1949. 4 in June 1951. 1 and 2 in November 1951. All scrapped

Card dimensions follow Alco’s April 1935 data card, class 442 S 280, order S-1740, supplied by Chris Hohl and digested by Steve Llanso, Locobase 106, together with the Milwaukee Road’s 1945 locomotive diagrams supplied by Allen Stanley. The May 21, 1936 outshopping of number 3 is Jim Scribbins, The Hiawatha Story. Information compiled September 28, 2026.

A 4-4-2 for 1935

Chicago to St. Paul was a three-railroad race. The Chicago & North Western put the 400 on in January 1935. The Burlington’s Zephyr followed in April. The Milwaukee had been hearing, since the fall of 1934, that its own answer was already on order: two streamlined Atlantics from Alco. The mechanical design was worked out with the railroad’s chief engineer, C. H. Bilty. Otto Kuhler designed the shroud.

An Atlantic looks like an odd choice for 1935. The type belonged to the turn of the century, and the Milwaukee’s own earlier 4-4-2s were Baldwin compounds, most of them gone by the early 1930s. Class A was a new engine. Four driving wheels kept the reciprocating weight down. The main rods drove the front axle. The drivers were 84 inches, so piston speed stayed reasonable when the train was at a hundred. A 300-pound boiler, one of the first conventionally staybolted boilers pressed that high, let the cylinders stay at 19 by 28 inches. Alfred Bruce, in The Steam Locomotive in America, credited that combination with a remarkably stable ride and called the four about the highest-speed steam locomotives yet built.

The railroad wanted a full-size train, cars that could be added or cut, and steam that could keep a six-and-a-half-hour schedule every day. Oil firing cut the servicing those speeds would otherwise have demanded. Milwaukee Shops built the cars: two six-car sets, each a Beaver Tail parlor-observation, a Tip Top Tap lounge, and coaches. The first engine was shown to the public on April 30, 1935. The second followed within a few days. Between May 5 and May 8, numbers 1 and 2 were in Chicago.

What Alco delivered

The April 1935 card is the specification the first two engines were built to. Heating surface is a firebox of 294 square feet, including 40 square feet of thermic syphons and arch tubes, on a grate of 69 square feet. There were 160 tubes of 2¼ inches and 43 flues of 5½ inches, 19 feet long. Evaporative surface is 3,245 square feet. The superheater is 1,029. Combined, 4,274. Tubes and flues account for 2,951 square feet of that evaporative total. The piston valves were 10 inches. Valve gear was Walschaerts. Every engine axle and every tender axle had roller bearings, and the cab was enclosed for the weather the timetable did not stop for.

On those proportions the four oil-burners were credited with more than 3,000 cylinder horsepower. That is a boiler figure, from the card. The timed speed is a different number, and it is below.

Specification	April 1935 Alco card
Alco class / order	442 S 280. Order S-1740. Railroad class A
Whyte / cylinders	4-4-2. Two simple cylinders, 19 × 28 in
Valve gear	Walschaerts. Piston valves 10 in
Drivers	84 in. Driver wheelbase 8 ft 6 in. Main rods on the front axle
Engine wheelbase	37.58 ft (37 ft 7 in)
Engine and tender wheelbase	78.87 ft (78 ft 10 in)
Boiler pressure	300 psi, conventionally staybolted
Tractive effort	30,685 lb. Factor of adhesion 4.70
Weight on drivers	144,300 lb
Engine weight	280,000 lb
Tender, loaded	247,000 lb. Water 13,000 gal. Oil 4,000 gal
Engine and tender	527,000 lb
Tubes	160, 2¼ in diameter, 19 ft long
Flues	43, 5½ in diameter, 19 ft long
Firebox	294 sq ft, including 40 sq ft of thermic syphons and arch tubes
Grate	69 sq ft
Evaporative heating surface	3,245 sq ft
Superheater	1,029 sq ft
Combined heating surface	4,274 sq ft
Bearings	Roller bearings on all engine and tender axles
Fuel	Oil

The published overall length is 88 ft 8 in over the couplers, and the published height is 14 ft 4 in. Those are the train’s outside dimensions. The wheelbases in the table are the card.

The 1945 diagram shows what a decade of Hiawatha running did to the tender. Oil capacity is up to 5,544 gallons. The loaded tender weighs 277,443 pounds. Engine and tender together weigh 563,443 pounds. Subtracting the tender leaves an engine of 286,000 pounds, six thousand pounds above the 1935 card. Water stayed 13,000 gallons. The grate, the 19-by-28-inch cylinders, the 84-inch drivers, and the 300-pound boiler are the same engine.

The 69 square feet on the card is the grate. The firebox heating surface is 294. Some published tables swap those two numbers.

The four engines

No.	Alco serial	Built	Retired	Notes
1	68684	May 1935	November 1951	Order S-1740. In Chicago with No. 2 between May 5 and May 8, 1935. Scrapped
2	68685	May 1935	November 1951	Order S-1740. Dynamometer run, May 15, 1935, 112.5 mph. Scrapped
3	68729	May 21, 1936	September 1949	Scribbins’s outshopping date. Withdrawn and used for parts. The Kindig photograph. Scrapped
4	68828	April 1937	June 1951	Last of the four. Photographed at West Milwaukee Shops, September 15, 1937. Scrapped

Order S-1740 is the April 1935 card, and the consecutive serials 68684 and 68685 belong to the first pair. Number 3 is serial 68729. Number 4 is 68828. Those later shop numbers are a separate piece of Alco work. A second order number for them was not on the 1935 card.

112.5 miles an hour

The railroad tested the new engines as soon as they were in Chicago. On May 15, 1935, number 2 ran with a dynamometer car and the original six-car train. Over 14 miles between Milwaukee and New Lisbon the speed was 112.5 miles an hour. The average for that trial was 74.9. In regular service the same trains averaged 80 to 81. At the time, 112.5 was the fastest authenticated steam speed on record, and number 2 was the first steam locomotive timed above 110.

Bruce wrote that on the runs which settled the timetable, the hand of the speed indicator was often against the pin at 128 miles an hour, and that the true maximum was never established. The figure that was timed is 112.5. The recognized steam record is LNER A4 Mallard’s 126 miles an hour, set in July 1938. The Milwaukee engines were built to cruise above 100 and to be capable of 120. The railroad’s own line, still carried on the Midwest Hiawatha page, said the oil-burning locomotive cruised easily at 100 miles an hour and was capable of two miles a minute.

Revenue service started on May 29, 1935. Trains 100 and 101, the Hiawatha, left Chicago and the Twin Cities on a daily 6½-hour schedule. The timing in the photograph’s caption is that schedule: 390 minutes. Published distances for the Chicago–St. Paul run of 1935 sit between 409 and 410 miles, depending on the terminal measured. With nine cars the same Atlantics later kept a 6¼-hour schedule over the 408 miles from Chicago through to Minneapolis. The June 1952 glance on the Hiawatha pages, about 6 hours 45 minutes and 421 miles, is that later timetable.

The six-car train grew as soon as people found it: seven cars, then eight, then nine. The name came from Longfellow, by way of Milwaukee employees and an Alco man. On January 21, 1939, a second Chicago–Twin Cities train went on, the Morning Hiawatha. The 1935 train became the Afternoon Hiawatha, still numbers 101 westbound and 100 eastbound.

Two minutes in Milwaukee

Kuhler’s shroud covered the boiler, the cab, and the tender, and left the running gear open along the bottom. The nose was a bullet, with a winged shield across it and the road number in the center of the wings. The tender carried the Hiawatha emblem. The colors were the train’s: maroon, gray, and orange. The casing was built to come open for the shop, and a pair of clamshell doors ahead of the smokebox gave access to the front end without dismantling the nose. In 1947 a Mars light was added under the winged emblem. That was the one visible change in twelve years.

Oil firing was the other half of the timetable. The stop at Milwaukee was water and passengers, and the railroad allowed two minutes for both. Then the train was moving again. A hundred miles an hour was ordinary running on the Chicago–Milwaukee lap and again on the flat country between Portage and Sparta. The schedule only worked if the station stops stayed that short.

Hudsons, then the torch

Nine cars were the edge of what a 4-4-2 was asked to do on that timing. In 1938 Alco delivered six Class F7 4-6-4s, numbers 100–105, streamlined by Kuhler on the same idea and fitted with the same 84-inch drivers. By 1939 the Hudsons were taking the nine-car Hiawathas. The Atlantics stayed in passenger service. On December 11, 1940, the Midwest Hiawatha went out behind 3 and 4, the pair that had been on the Twin Cities trains, with a six-car consist of its own on the Omaha main.

Diesels took the streamliners after the war. Number 3 was withdrawn in September 1949 and stripped for parts so the other three could finish. In December 1950 a Class A was still on secondary passenger work, leaving Madison, Wisconsin, with eastbound train 14, the On Wisconsin, for Chicago: coaches, a diner, a buffet-parlor, a lounge, and a parlor-solarium. Number 4 went in June 1951. Numbers 1 and 2 went in November 1951. All four were scrapped. The steam roster’s retirement cell for the class, 1949 and 1951, is that span. What the Hiawatha became after the Atlantics is on the train’s own page, and the rest of the Milwaukee’s post-1900 steam is on the steam roster.

Sources

American Locomotive Company data card, class 442 S 280, order S-1740, April 1935, supplied by Chris Hohl (January 29, 2026) and digested by Steve Llanso, Locobase 106, on steamlocomotive.com. Driver, cylinder, valve, heating-surface, weight, and tender figures for the as-built engine, including Walschaerts gear, 10-inch piston valves, roller bearings, and 40 square feet of thermic syphons and arch tubes. The same entry credits the design with more than 3,000 cylinder horsepower.
Chicago, Milwaukee, St. Paul & Pacific, 1945 locomotive diagrams, supplied by Allen Stanley (Rail Data Exchange) and quoted in that Locobase entry: tender oil 5,544 gallons, tender 277,443 lb, engine and tender 563,443 lb.
Bruce, Alfred W. The Steam Locomotive in America. 1952. Pp. 292–293, as quoted by Locobase: 19 × 28 cylinders, 84-inch drivers, 300 psi, main rods on the front axle, a staybolted boiler at 300 pounds, the stable ride, and the untimed 128 mph indicator reading.
Scribbins, Jim. The Hiawatha Story. Number 3 outshopped from Alco on May 21, 1936, and the schedule in the Kindig caption.
Trains, “Milwaukee Road’s A-class: ultimate 4-4-2,” January 12, 2025. Four engines, 1935, 1936, and 1937. Number 4 at West Milwaukee Shops, September 15, 1937. Oil fuel, 84-inch drivers, roller bearings, all-weather cabs, main rods on the first driving axle, about 144,300 pounds on the drivers. The 390-minute schedule for a run of about 410 miles. Class F7 Hudsons from Alco in 1938.
Published class roster for serials and retirement months: 1, serial 68684, May 1935, November 1951; 2, serial 68685, May 1935, November 1951; 3, serial 68729, May 1936, September 1949, then used for parts; 4, serial 68828, April 1937, June 1951. Overall length 88 ft 8 in. Height 14 ft 4 in. Mars light under the winged nose emblem, 1947. Designed to cruise above 100 mph and to reach 120. May 15, 1935, number 2, 112.5 mph over 14 miles between Milwaukee and New Lisbon.
German-language class account (MILW-Klasse A): the design worked out with chief engineer C. H. Bilty; first engine shown April 30, 1935; the second a few days later; twelve cars built at Milwaukee Shops for two trainsets.
Milwaukee Road passenger pages on this site, for the operating record already in print: inauguration May 29, 1935, trains 100/101; six cars, then seven, eight, and nine; May 5–8 arrival of 1 and 2; trial average 74.9 mph and 80–81 mph in regular service; Morning Hiawatha, January 21, 1939; Midwest Hiawatha, December 11, 1940, behind 3 and 4; the December 1950 On Wisconsin departure from Madison.

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