Southern Pacific class MC-4

Southern Pacific Railroad's MC-4 class of steam locomotive was the second class ordered and built as cab forward locomotives. Southern Pacific (SP) found the MC-2 class sufficient for a proof-of-concept for cab forward locomotives and sought to continue with now tested designs.

Southern Pacific class MC-4
Type and origin
Power typeSteam
BuilderBaldwin Locomotive Works
Serial number36490-36493, 36524-36527, 36614-36616, 36634
Build dateApril–May 1911
Gauge4 ft 8 12 in (1,435 mm) standard gauge
Driver dia.57 in (1,448 mm)
Adhesive weight398,500 lb (180,800 kg)
Loco weight432,600 lb (196,200 kg)
Boiler pressure200 psi (1.4 MPa)
High-pressure cylinder26 in × 30 in (660 mm × 762 mm)
Low-pressure cylinder40 in × 30 in (1,016 mm × 762 mm)
Performance figures
Tractive effort85,040 lbf (378.28 kN)
OperatorsSouthern Pacific Railroad
Numbers4017 4028
First runJuly 21, 1911
Retired1947 1948

In service, SP found that the locomotives were a little too slow for the traffic needs. By 1930, all of the MC-4 class had been "simpled" to use uniform size cylinders and feedwater heaters were installed to address the issue. They were then reclassified as AC-2 locomotives. As rebuilt, the locomotives continued in service through the end of World War II.


  • Diebert, Timothy S. & Strapac, Joseph A. (1987). Southern Pacific Company Steam Locomotive Conpendium. Shade Tree Books. ISBN 0-930742-12-5.
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