Southern Pacific class AC-2

Southern Pacific Railroad's AC-2 class of steam locomotives was the second in the AC series of cab forward locomotives built for Southern Pacific (SP). This class consisted of locomotives that were rebuilt from Baldwin-built SP MC-4 class locomotives by 1930.

Southern Pacific class AC-2
Type and origin
Power typeSteam
Gauge4 ft 8 12 in (1,435 mm) standard gauge
Driver dia.57 in (1,448 mm)
Adhesive weight440,800 lb (199,900 kg)
Loco weight481,200 lb (218,300 kg)
Boiler pressure210 psi (1,400 kPa)
Feedwater heater4¼-BL Worthington
Cylinder size22 in × 30 in (559 mm × 762 mm) dia × stroke
Performance figures
Tractive effort90,940 lbf (404.5 kN)
OperatorsSouthern Pacific Railroad
Number in class12
Numbers4017 4028
Retired1947   1948

The rebuild from MC-4 class gained the locomotives about 5,000 pounds-force (22 kN) in tractive effort, but also increased the locomotives' weight by about 50,000 pounds (23,000 kg). The locomotives were deemed successful and remained in active service until after 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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