Southern Pacific class AC-3

Southern Pacific Railroad's AC-3 class of steam locomotive was the 3rd and last cab forward design based on the 2-8-8-2 wheel arrangement. All 20 locomotives in this class were rebuilds from MC-6 class locomotives originally built by Baldwin Locomotive Works in 1912 and 1913. The rebuilds all took place in the late 1920s at Southern Pacific's Sacramento shops.

Southern Pacific class AC-3
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) in dia × stroke
Performance figures
Tractive effort90,940 lbf (404,500 N)
OperatorsSouthern Pacific Railroad
Number in class20
Numbers4029 4048
Retired1948 1949

After the rebuilds, these locomotives were used through World War II. The first to be retired from active service were numbers 4040 and 4045, both on October 21, 1946; the last to be retired was number 4032 on August 8, 1949. The AC-3ś were Used for Long Freight Runs, and sometimes even Used to pull Passenger/Troop Cars during World War II. All of this class were scrapped soon after retirement.


  • 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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