Milwaukee Road 2-6-2 "Prairie" Locomotives in the USA

Class K1 (Locobase 815)

Data from MILWRD 1930ca Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange collection and Fowler (Ed.), 1912 Locomotive Cyclopedia (New York: Simmons-Boardman Co, 1912), p. 201. See also Jim Scribbins, "Chicago, Milwaukee, St Paul & Pacific (Milwaukee Road)" in George H Drury, Guide to North American Steam Locomotives, Revised Edition (Waukesha, WI: Kalmbach Books, 2015), p. 134. (Thanks to Chris Hohl for his 13 December 2020 email querying the firebox heating surface areas and supplying the tender's coal capacity.) Works numbers were 43853-43893 in October 1907, 43894-43902 in November, 45427-45461 in August 1908, 45462-45476 in September, 45815-45816 in January 1909, and 45817-45839 in February.

Brooks built 125 of these very useful Prairie freight locomotives from 1907-1909, and the Milwaukee Road's (then the Chicago, Milwaukee, & St. Paul) own West Milwaukee shops completed another 70. The first fifty were sent to Lines West (Chicago, Milwaukee & Puget Sound), the recently begun extension of the Milwaukee from South Dakota to the West Coast. 95 of the next 145 also ran under the CM&PS herald.

Jim Scribbins wrote they burned lignite coal (low-calorie, therefore requiring a large firebox) but were otherwise intended to haul the same train load between Minneapolis and Harlowton, Mont that earlier 4-6-0s had worked from Chicago to Minneapolis. The coal came from Roundup, Mont., along the main line and thus essentially a captive source. In the event, K1s worked about 250 miles (400 km) further west to Alberton, Mont, northwest of Missoula and close to the Idaho border. In the more mountainous sections, K1s would triple-head a train.

Before very long, however, K1s ranged over the whole system on branchline and local service. In comparison with the railroad's 4-6-0 freight engines, whose fireboxes lay between the frames and over the last 1 1/2 driving axles, he K1's drivers sat below and ahead of the firebox. Between the firebox itself and the rear tubesheet, a short combustion chamber contributed 52 sq ft (4.83 sq m) to the firebox heating surface area. Arch tubes placed in the combustion chamber added 27 sq ft (2.51 sq m).

The 125 that weren't superheated were retired in the late 1930s. For the 70 superheated engines, see Locobase 6795.

Class K1-as (Locobase 6795)

Data from Milwrd 1930a Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also Jim Scribbins, "Chicago, Milwaukee, St Paul & Pacific (Milwaukee Road)" in George H Drury, Guide to North American Steam Locomotives, Revised Edition (Waukesha, WI: Kalmbach Books, 2015), p. 134.

As big a holding as the Milwaukee had in Prairies (Locobase 815), it only made sense to superheat them. Abou 30% received the new equipment. Road numbers 5002, 5004, 5007, 5013, 5021-5022, 5032, 5037-5041, 5044, 5501,5503, 5506-5508, 5513, 5523, 5526, 5532, 5534, 5538, 5540, 5544, 5548, 5550, 5555, 5557, 5561, 5563-5567, 5569, 5575, 5583, 5587-5588, 5593-5595, 5598-5599, 5602-5603, 5605, 5209-5610, 5621, 5626, 5641, 5643.

The firebox heating surface included 27 sq ft of arch tubes and an unusually precise 43.26 sq ft (4.02 sq m) in a short combustion chamber. Piston valves measured 12" (305 mm) in diameter.

Not all of the superheated engines were renumbered in the 900 series in 1938, but all ran on Milwaukee metals until the late 1940s and early 1950s.