2-8-8-4 "Yellowstone" Locomotives in the USA

Northern Pacific Yellowstone

Only 72 Yellowstones were built (in five different classes). Each class of Yellowstone was a different design (except for the two classes owned by the DM&IR). The design was usually dictated by the specific needs of the railroad that received them.

Northern Pacific class Z-5

The first Yellowstone was built in 1928 by ALCO for the Northern Pacific for running throughout the high speed plains of North Dakota. It would turn out to be the one and only Yellowstone that ALCO would build.

NP wanted to burn low-grade Rosebud coal (obtained from mines along the line) in their locomotives. This required the Yellowstone to be designed with a huge (the largest ever used on a steam locomotive) firebox (182 sq. ft.). The front half of the firebox was over the two rear pairs of drivers and the trailing truck (which was equipped with a booster).

It was the largest steam locomotive in the world (at that time) and ALCO celebrated by serving dinner to 12 people seated in the firebox! NP asked for bids for 11 more like it and in 1930 Baldwin got the job. The NP Yellowstones steamed poorly and produced less that 5,000 HP. NP found that the grates were simply too large to maintain a high temperature and complete combustion. The combustion problem was solved by blocking off The front two feet of the firebox on each locomotive. At some point the Z-5s were upgraded with roller bearings.

Southern Pacific class AC-9

Most of Southern Pacifics "big steam" were of the Cab Forward design (a backwards Yellowstone). However, not all of the SP "big steam" was required to run through the snow sheds of the Sierras. In 1939 the SP received 12 Yellowstones from Lima for use throughout the southern part of the SP system. Unlike the Cab Forwards, the class AC-9 locomotives were built as coal burners. They were later converted to burn oil. Also, the AC-9 class had a grate area of 146 sq. ft. rather than the 139 sq. ft. of their cab forward siblings. With their skyline casings and striped cowcatcher-pilots, they could almost be considered streamlined. They were retired between 1953 and 1956.

Duluth, Missabe & Iron Range classes M-3 and M-4

In the late 1930s the DM&IR was in need of new locomotives that would be able to handle 115-car, 8750-ton trains over .62% grades without stalling. The Western Pacific 2-8-8-2 was used as a basis for its design. The larger cab required a longer and heavier frame, therefore a 4-wheel trailing truck was used. Roller bearings were used on all locomotive and tender axles. The DM&IR was the only road who chose to use "pedestal" or "centipede" tenders with their Yellowstones. THE DM&IR Yellowstones also had gray boiler jacketing.

DM&IR was pleased with the first batch (class M-3) of 8 received from Baldwin in 1941 so they ordered 10 duplicates (class M-4). They were completed late in 1943 after much of DM&IR's traffic had subsided, so some of the M-4s were leased by and delivered directly to the Denver & Rio Grande Western. The following winter the D&RGW again borrowed the 2-8-8-4s for use as helpers over the 10,239-foot Tennessee Pass crossing of the continental Divide. The D&RGW sent a telegram to the DM&IR stating that the Yellowstones were the finest steam locomotives to ever operate on its road.

On the DM&IR they were used as the main road power to pull ore trains throughout the Duluth area. For the most part, ore trains had to be pulled downhill to the ore docks on Lake Superior in Duluth and Two Harbors. These trips did not require the enormous pulling force of the Yellowstones. Surprisingly, the limiting factor (as far as what the iron range locomotives could pull) was the 2.2 percent grade from Duluth up to the yards in Proctor. The ore cars had to be returned empty to these yards for sorting.

The Yellowstones were sometimes used to pull empties up this hill from Duluth to Proctor. However, the classic 'hill' power was the older modified 2-8-8-2 'Hill' engines with their extra air tanks on top of the boiler. Newer 2-10-4s and 0-10-2s were also used on the 'Hill' at least in the mid-late 50's when steam was still on the line. Someone once told me that he spoke to a couple people (including the diesel shop foreman who used to fire the Yellowstones and a former engineer on the Yellowstones) at the Proctor roundhouse while 227 was being restored in preparation for its display in the museum in Duluth. They said that it was possible to empty the tender of almost all coal and water of a Yellowstone while pulling a load of empty ore cars up the hill from Duluth to Proctor. This is to say: 25,000 gallons water and 25-26 tons of coal! This is hard to believe and perhaps it is a bit of an exaggeration, but it does show that this was one of the more difficult tasks for the Yellowstones.

All of the DM&IR Yellowstones were all retired between 1958 and 1963.

Baltimore & Ohio class EM-1

The EM-1s were the last articulated steam locomotives built for the B&O. Actually, the B&O did not want the EM-1s. Instead they wanted diesels. However, because of restrictions imposed by the War Production Board, the EM-1s were delivered from Baldwin in 1944 (7620 - 7619) and 1945 (7620 - 7629). For this wheel arrangement, they were relatively modest in size, but very successful. Originally, they worked on the Cumberland Division, a very physically difficult stretch of the B&O, with numerous heavy coal trains, as well as fast freights. The main district served by the EM-1 was the line from Cumberland towards Grafton, WV. Later, as diesels took over this assignment, the class was shifted to the Pittsburgh Division, where they primarily handled Lake Mineral traffic, plus trains between Wheeling and Pittsburgh. The class was renumbered 650-679. They started to be scrapped in 1957, and all were off the roster by 1960.

A Comparison of Yellowstone Designs

This table compares the various Yellowstone designs along with that of the UP Big Boy and Western Pacific 2-8-8-2 . All Yellowstone classes employed simple steam expansion and thus none can be called "mallets".

Type NP
Series 5000 3800-3811 220-237 228-237 7600-7619 4000-4019 251-260
Cyl:dia x stroke 26x32 24x32 26x32 26x32 24x32 23.75x32 26x32
Driver diameter 63 63.5 63 63 64 68 63
Boiler pressure 250 250 240 240 235 300 250
Grate area 182 139.3 125 125 117.5 150 145
Evaporative heating surface 7673 6918 6780 6758/6780 5298 5889
Superheater heating surface 3219 2831 2770 2770 2118 2466
Weight on drivers 554,000 531,200 560,257 564,974 485,000 540,000 552,700
Total engine weight 715,000 689,900 695,040 699,700 628,700 762,000 665,100
Tender weight 401,000 400,700 436,635 438,335 382,000 427,500 408,250
Tractive force engine 145,930 124,300 140,000 140,000 115,000 135,375 137,000
Tractive force booster 13,400 None None None None None 13,900

Railroads that used 2-8-8-4 "Yellowstone" locomotives in USA (data provided by Steve Llanso of Sweat House Media)

Surviving Examples of 2-8-8-4 "Yellowstone" Locomotives in the USA

No. Class F.M. Whyte Gauge Railroad Line Location Status Builder Info Notes
227 M-3 2-8-8-4 4'-8½" DM&IR Lake Superior Railroad Museum, Duluth, MN display Baldwin #62533, 1941
225 M-3 2-8-8-4 4'-8½" DM&IR US 2, Proctor, MN display Baldwin #62531, 1941
229 M-4 2-8-8-4 4'-8½" DM&IR D&IR Depot, Two Harbors, MN display Baldwin #64708, 1943

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