The DM&IR’s Yellowstones, classified
as M-3s and M-4s and built by Baldwin (there was no difference in the
two classes save for they were ordered at different times), were used
primarily for the railroad’s heavy ore services that it was so well
known for. The latest built, Class M-4, were delivered in 1941 but
survived barely twenty years before the final one was parked in 1961.
Lastly, the B&O’s EM-1 Class was lucky to have been built at all.
Thirty of these locomotives would be built and were delivered to the
B&O (from Baldwin) at the end of World War II between 1944 and 1945.
One interesting note is that the B&O actually wanted and
would have preferred newer diesel technology for this latest locomotive
order and not steamers. However, because the country was in the middle
of WWII diesel-electric construction had been halted to focus on the war
effort and was not available for purchase. Likewise, the B&O (as
did almost all of the railroads during this time) needed locomotives and
lots of them to keep up with the blizzard of demand during wartime and
so they settled on the next best thing, a well designed steam
Railroads Operating Yellowstones
· Baltimore & Ohio Railroad, Class EM-1: 30
· Duluth, Missabe & Iron Range Railway, Class M-3: 8
· Duluth, Missabe & Iron Range Railway, Class M-4: 10
· Northern Pacific Railway, Class Z-5: 12
· Southern Pacific Railroad, Class AC-9: 12
And well built the locomotive was. It had a rather low boiler pressure comparative to other models in its class but this low pressure had a great benefit, a high factor of adhesion (4.22). This high ratio allowed the locomotive to start rather efficiently in that it was not as susceptible to wheel slippage as other designs. For instance, this added incentive was an extra benefit in the type of service the B&O originally designated the EM-1, the torturous grades of the railroad’s West End (its Cumberland Division), through the Appalachians. The locomotive did a marvelous job at this, having little trouble hauling merchandise or coal drags over the steep climbs of Cranberry Grade, along the West Virginia/Maryland border, or over Sand Patch in Pennsylvania.
As you can see, all Yellowstones were built for essentially one
reason, to move heavy traffic over steep grades as efficiently as
possible. And, even though the steamers would become the most
technologically advanced ever developed they still could not reach the
efficiencies of new diesel-electric technology and all were retired by
1960. In any event, they did their duty quite well, so well in fact
that the Denver & Rio Grande Western Railroad, upon borrowing a few
from the DM&IR considered them the very best steam locomotives the
railroad had ever operated! While not every class survives today a few
have been preserved, including at least three of the DM&IR’s
Yellowstones; 225, 227, and 229.
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