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
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.