The Chicago, Milwaukee, St. Paul & Pacific Railroad's own motive power
department designed a Class S-1, 4-8-4 in 1930. It was built by the Baldwin
Locomotive Works and put on the roster as number 9700. It remained the lone
Northern on the CMStP&P for the next seven years. A second one-of-a-kind
was built in 1938 in CMStP&P's own shops in Milwaukee, WI. This was also
a Class S-1 and was given road number 251. At this time number 9700 was
In 1937, an order of 30 Class S-2s was delivered from Baldwin. These were
given road numbers 201 through 230. A second order of 10 Class S-2s were
delivered from Baldwin in 1940 (road numbers 231 through 240). The Class S-2
Northerns weighed 490,450 lbs, had 74" drivers, 26 x 32 cylinders, 285 lbs
psi and had a tractive effort of 70,800 lbs.
Because of wartime needs, another order of 10 (road numbers 260 through 269)
Class S-3 Northerns was delivered in 1943 from the American Locomotive
Company. This class was designed to have 74" drivers, 26 x 32 cylinders, 250
lbs psi boiler pressure and weighed 460,000 lbs and had a tractive effort of
There are two survivors: number 261, which is operational and number 265 at
the Illinois Railway Museum in Union, IL. When 261 is not running, it is
stored at the old GN Shops near Minneapolis Junction in Minneapolis, MN.
Class S1 (Locobase 247)
Data from 1930 Locomotive Cyclopedia tables. Also see Steve Glischinski's article on the MIlwaukee's generations of 4-8-4s at http://www.261.com/history/generations.shtml
, last accessed 23 September 2007.
As with most Class 1 locomotives built in this period, the firebox's heating surface area included a variety of structures and supplements. The combustion chamber contributed 122 sq ft (11.3 sq m), thermic syphons (two in the firebox, one in the combustion chamber) 116.5 sq ft (10.8 sq m) and arch tubes 16.5 sq ft (1.5 sq m). The boiler's Coffin feedwater heater was to be "applied in recess provided in smoke box.". The 14" piston valves had 9" of travel.
This was the proof-of-concept Northern for the Milwaukee Road, Glischinski's account says that 9700 (works #61176 in December 1929) entered service in 1930 from Baldwin as a trial horse against the powerful F6 4-6-4s then in service. He contends that the S1 was a stretched F6 in any case. Baldwin called it a "Modified Mountain".
For the moment, the Milwaukee's passenger trains made do with the F6 and the 9700 was put to work pulling 5,000-ton freights on its own. In 1934, the 9700 began working passenger trains between Avery, Idaho and Othello, Washington. In February 1938, the West Milwaukee shops duplicated the 9700, by then renumbered 250, and rolled out the 251. (Glischinski notes that it was the last new locomotive from that facility.)
Class S2 - circulator (Locobase 248)
Data from 1947 Locomotive Cyclopedia table and diagram and from MILWRD 1945 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection. (Thanks to Chris Hohl for a correction of the boiler pressure.) Works numbers were 62092 in October 1937 and 62344, 62346 in March 1940; 62345, 62347 in April; 62348-62353 in May.
Engines 203 and 231-240 used 105.5 sq ft (9.8 sq m) of circulators to supplement firebox heating surface instead of the 147 sq ft (13.65 sq m) of thermic syphons installed in the rest. See the photo provided on 16 September 2008 by "Mark D" to the Chaski Forum http://www.chaski.org/railfan/viewtopic.php?f=2&t=835; it illustrates splendidly the arrangement of the tubes and the firebricks that lay on top of them. The firebox also had a combustion chamber.
These forty S-2s operated mostly as freight haulers from Bensenville to Council Bluffs, Iowa or St. Paul, Minn. Occasionally they'd hook up to the westbound Olympian if it trailed more than twelve cars.
Class S2 - thermic syphon (Locobase 11085)
Data from MILWRD 1945 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection. . Works numbers were works numbers 62089-62091 in October 1937, 62093-62095 in November, 62096-62102 in December, 62103-62110 in January, 62111-62116 in February, and 62117 in March.
Even before theWest Milwaukee shops produced the 251 (see Locobase 247), the Milwaukee Road had gone to Baldwin for its definitive Northerns. The first 28 were produced in October 1937 through February 1938
147 sq ft of thermic syphons contributed to the firebox heating surface as did the combustion chamber. They had 14" piston valves with 7 1/2" of travel. Engines 203 and 231-240 used 105 sq ft of circulators to supplement firebox heating surface; see Locobase 248 for the data.
These S-2s operated mostly as freight haulers from Bensenville (West Milwaukee) to Council Bluffs, Iowa or St. Paul, Minn. Occasionally they'd hook up to the westbound Olympian if it trailed more than 12 cars.
Class S3 (Locobase 249)
Data from 1947 Locomotive Cyclopedia tables. Also see Steve Glischinski's article on the MIlwaukee's generations of 4-8-4s at http://www.261.com/history/generations.shtml
, last accessed 23 September 2007.
Firebox heating surface included 80.5 sq ft of circulators.
The last of the Milwaukee Road's Northerns, this design pieced together a Rock Island frame, a Delaware & Hudson boiler, and a Union Pacific tender. Like the 1940 batch from Baldwin, the boiler used circulators in place of thermic syphons. Glischinski's account says of this batch "...an Alco ad touted them as 'the last word in 4-8-4 design.' They featured roller bearings, special compensating lateral driving-box devices, and precision firing equipment."
Four were later converted to oil-burning and the engines saw out steam in both freight and passenger service with retirements coming in 1954-1956.