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Duluth, Missabe & Iron Range 2-8-8-4 "Yellowstone" #229 as preserved.

Under the Whyte notation a 2-8-8-4 is a steam locomotive with two leading wheels, two sets of eight driving wheels, and a four-wheel trailing truck.

Other equivalent classifications are:

The equivalent UIC classification is, refined for Mallet locomotives, (1′D)D2′.

Such a long locomotive must be an articulated locomotive, and all the examples produced were Mallets, with a joint in the frame between the first and second groups of driving wheels. The superstructure of the locomotive was attached to the rearmost set and the forward set and leading truck could swing laterally on curves.

The type was generally named the Yellowstone, a name given it by the first owner, the Northern Pacific Railway, whose lines run near Yellowstone National Park. Seventy-two Yellowstone type locomotives were built for four different US railroads.

The 2-8-8-4 was a common arrangement for the largest steam locomotives. All Yellowstones had fairly small drivers of 63 to 64 inches (1.60 to 1.63 m). For greater speeds, the Union Pacific Railroad chose a four-wheel leading truck and 68 inches (1.73 m) drivers for its Big Boy 4-8-8-4 class.

Several classes of Yellowstone, especially the Duluth, Missabe and Iron Range's locomotives, are among the largest steam locomotives, with the exact ranking depending on the criteria used.


  • Northern Pacific 1
  • Southern Pacific 2
  • Duluth, Missabe and Iron Range 3
  • Baltimore and Ohio 4
  • Outside the United States 5
  • Notes 6
  • References 7
  • External links 8

Northern Pacific

The Northern Pacific Railway was the first railroad to order a 2-8-8-4. The first was built in 1928 by ALCO; it was the largest locomotive built until then, and it had the largest firebox ever applied to a steam locomotive, some 182 square feet (16.9 m2) in area. The purpose was to burn Rosebud coal, a cheap low-quality coal. That firebed was too large for the available draft and the fire burned poorly. The problem was mitigated by blocking off the first few feet of the grates. Baldwin built eleven more for the NP in 1930.

Southern Pacific

The Southern Pacific Railroad's famous "cab-forward" articulated steam locomotives were effectively a Yellowstone in reverse, but the SP also owned some conventional 2-8-8-4s for use on its less mountainous routes. Lima built twelve AC-9 class locomotives in 1939; they had skyline casings with striped pilots. At first they burned coal but were later converted to oil firing.

Duluth, Missabe and Iron Range

The Duluth, Missabe and Iron Range Railway hauled iron ore in Minnesota. Iron ore is heavy and the DM&IR operated long trains of ore cars, requiring maximum power. These locomotives were based upon 10 2-8-8-2s that Baldwin had built in the 1930s for the Western Pacific Railroad. The need for a larger, coal burning firebox and a longer, all-weather cab led to the use of a four-wheel trailing truck, giving them the "Yellowstone" wheel arrangement. They were the most powerful Yellowstones built, producing 140,000 lbf (620 kN) of tractive effort, and had the most weight on drivers so that they were not prone to slipping.

Eight locomotives (class M-3) were built by Baldwin in 1941. The Yellowstones met or exceeded the DM&IR specifications so ten more were ordered (class M-4). The second batch was completed late in 1943 after the Missabe's seasonal downturn in ore traffic, so some of the new M-4s were leased to and delivered directly to the Denver & Rio Grande Western.

A tourist views Duluth, Missabe & Iron Range 2-8-8-4 "Yellowstone" preserved at Two Harbors, Minnesota, 2004.

The next winter the D&RGW again leased the DM&IR's Yellowstones as helpers over Tennessee Pass, Colorado and for other freight duties. The Rio Grande returned the Yellowstones after air-brake failure caused Number 224 to wreck on the Fireclay Loop.[1] This was despite the Rio Grande's earlier assessment that these Yellowstones were the finest engines ever to operate there.

DM&IR's were the only Yellowstones to have a high-capacity pedestal or centipede tender, and had roller bearings on all axles. Some of the locomotives had a cylindrical Elesco feedwater heater ahead of the smoke stack, while others had a Worthington unit with its rectangular box in the same location.

Only one Yellowstone was retired before dieselization took place on the Missabe; Number 237 was sold for scrap after a wreck. The rest of the 2-8-8-4s were retired between 1958 and 1963 as diesel locomotives took over.

Three of the eighteen built still survive and are on display: Number 227 at the Lake Superior Railroad Museum in Duluth, Minnesota, Number 225 in Proctor, Minnesota, and Number 229 in Two Harbors, Minnesota.

Baltimore and Ohio

B&O EM-1 2-8-8-4 Yellowstone
Type and origin
Power type Steam
Builder Baldwin Locomotive Works
Build date 1944 (20) 1945 (10)
Total produced 30
Configuration 2-8-8-4
UIC classification (1′D)D2′
Gauge 4 ft 8 12 in (1,435 mm) standard gauge
Leading wheel
30 in (762 mm)
Driver diameter 64 in (1,626 mm)
Trailing wheel
38 in (965 mm)
Wheelbase 81 ft 6.7 in (24.86 m)
Length Locomotive: 83 ft 2.9 in (25.37 m)
Overall: 128 ft 8 in (39.22 m)
Width 11 ft (3.353 m)
Height 16 ft (4.877 m)
Weight on drivers 485,000 lb (220,000 kg; 220 t)
Locomotive weight 627,000 lb (284,000 kg; 284 t)
Tender weight 328,000 lb (149,000 kg; 149 t)
Locomotive and tender
combined weight
1,010,700 lb (458,400 kg; 458.4 t)
Fuel type Coal
Fuel capacity 25 short tons (22 long tons; 23 t)
Water capacity 22,000 US gal (83 m3)
Boiler 94 18 in (2.39 m) dia.
Boiler pressure 235 psi (1.62 MPa)
Feedwater heater Worthington
Firegrate area 117.5 sq ft (10.92 m2)
Heating surface:
– Firebox
228 by 96 in (5.79 by 2.44 m) with a 90 in (2.29 m) long combustion chamber
Superheater type Type "E"
Cylinders Four
Cylinder size 24 by 32 in (610 by 813 mm)
Performance figures
Tractive effort 115,000 lbf (510 kN)
Factor of
Operator(s) Baltimore & Ohio Railroad (B&O)
Class EM-1
Number(s) 7600–7629 later 650–679
Last run April 19, 1960
Preserved 0
Disposition All thirty scrapped by 1960.

When the U.S. entered World War II The American railroads saw increases in traffic. The Baltimore and Ohio Railroad, along with other railroads, wanted to purchase more of the diesel locomotives since they were showing improved performance over steam locomotives. But the War Production Board regulated the production of steam and diesel locomotives until the war emergency was over. So along with producing 40 new class T-3 4-8-2 type locomotives in-house at their Mt. Clare shops in Baltimore, Maryland, the B&O took delivery of 30 class EM-1 Yellowstones in 1944 and 1945, the largest number and the smallest of this type built by Baldwin as well as the most modern.

The EM-1 produced 115,000 pounds-force (510 kN) of tractive effort on 64-inch (1.6 m) drivers with 235 pounds per square inch (1.62 MPa) steam pressure and four 24-by-32-inch (0.61 by 0.81 m) cylinders. The tender carried 22,000 US gallons (83 m3) of water and 25 tons of coal. The engine weighed 627,000 pounds (284 t) while the tender weighed 328,000 pounds (149 t) for a combined 1,010,700 pounds (458.4 t). Nothing bigger could operate within the tunnel clearances and track restrictions on the B&O's main line.

They were equipped with the newest technology including the Worthington feedwater heater, superheater with front-end throttle, Cyclone front end, thermic syphons, a lateral cushioning device in the front pair of drivers on both engines and the front wheels and the trailing truck, as well as roller bearings on all axles, engine and tender, which gave them the reputation of "yard creepers", because three men could move one on a level track with the cylinder cocks open.

B&O's president, Roy B. White, after inspecting the first one delivered, said to the general superintendent of motive power and equipment, A.K. Galloway, "well, I must say, they have everything!"

Fleet numbers 7600–7619 were built and delivered in 1944 and 7620–7629 in 1945, all by the Baldwin Locomotive Works of Philadelphia, Pennsylvania. They went to work on the Cumberland Division's rugged West End subdivision with its more than 2% grades and tight curves where with the older 2-8-8-0 EL classes hauled West Virginia coal and freights. Since the EM-1s had roller bearings throughout, they also handled mail and express trains, replacing two B&O class T-3 4-8-2 Mountains. That continued until January 21, 1947 when near Oakland, Maryland, train 29 with engine 7625 derailed with the locomotive rolling onto the engineer's side, killing the engineer. The EM-1s were then restricted to coal and freight trains until the late 1950s, when the B&O used EM-1 No. 7600 for railfan trips.[2]

The EM-1s also ran on the Pittsburgh Division over Sand Patch Grade near Meyersdale, Pennsylvania, with empty hoppers, iron ore or dolomite loads westbound, coal eastbound, as well as general freight in both directions. In the late 1950s, the B&O used EM-1 No. 7600 for railfan trips mostly between Cumberland, MD, and Connellsville, PA. Well-known photographer and Cumberland, MD, native William P. Price captured on still pictures and 8mm films, the EM-1s on the east side of Sand Patch pulling heavy trains with two of the B&O's 2-10-2 class S1 and S1a Big Sixes on the rear as helpers dispatched from Hyndman, PA.

Near the end of steam they were all sent out to Fairmont and Wheeling, West Virginia, and Lorain, Ohio, with lake-bound coal trains as well as runs between Willard, OH and Garrett, Indiana, until the B&O started to retire them in 1957. As good as they were, they could not compete with the diesels. None were saved from the scrapper's torch.[3]

Outside the United States

The metre gauge Central Railway of Brazil took delivery of four 2-8-8-4s from the German firm of Henschel in 1937. They were the only narrow gauge locomotives of this wheel arrangement, but not the only 2-8-8-4s outside the United States, they had the largest boilers ever used on a narrow-gauge Mallet.

Soviet Russia constructed two 2-8-8-4 locomotives at the Kolomna Locomotive Works. These were the P38 Class numbers P38.001 and P38.002. The first locomotive carried partial casings over the boiler and smokebox typical of the 1950s. P38.002 bore no such adornments and had a more conventional appearance. Both engines had tenders with part bogie and part fixed frame similar to the American 'centipede' tenders.[4]


  1. ^ LeMassena, R. (2000). "David Moffat’s Double Dilemma", in 'The Railway & Locomotive Historical Society Newsletter', Volume 20, Number 2, Sacramento: Railway & Locomotive Historical Society.
  2. ^ Roberts, Charles S, "West End, Cumberland to Grafton 1848–1991." Baltimore, MD Barnard, Roberts & Co. Inc. Second Edition (2001) ISBN 0-934118-18-3
  3. ^ Sagle, Larry and Stauffer, Alvin "B&O Power, Steam, Diesel and Electric Power on the Baltimore & Ohio Railroad." Eighth printing (1984) LCCN 64-23526
  4. ^ Rakov. V.A. Locomotives of the Russian and Soviet Railways - Vol 1 - 1845 to 1955 Moscow-1995


  • Barris, W. The Yellowstone Type Locomotive. Retrieved January 4, 2003, from
  • Westcott, L. (Ed.). (1960). Model Railroader Cyclopedia Volume 1: Steam Locomotives. Waukesha, WI: Kalmbach. ISBN 0-89024-001-9
  • Roberts, Charles S, "West End, Cumberland to Grafton 1848–1991." Baltimore, MD Barnard, Roberts & Co. Inc. Second Edition (2001) ISBN 0-934118-18-3
  • Sagle, Larry and Stauffer, Alvin "B&O Power, Steam, Diesel and Electric Power on the Baltimore & Ohio Railroad." Eighth printing (1984) LCCN 64-23526
  • Dixon Jr., Thomas W. and Withers, Bob. "Baltimore & Ohio's Magnificent 2-8-8-4 EM-1 Articulated Locomotive." (2007) TLC Publishing, Forest, VA. ISBN 0-939487-83-7
  • Brown, John K. "The Baldwin Locomotive Works- A Study in American Industrial Practice" Johns Hopkins University Press. 1995.

External links

  • 2-8-8-4 or Yellowstone
  • The Yellowstone Type Locomotive
  • Web Site of ToyTrains1 2-8-8-4 Yellowstone Steam Locomotives
  • , July 1930Popular Mechanics Monthly"Is This Monster Locomotive a HE or SHE?"
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