Southern Pacific class AC-7

Southern Pacific Railroad's AC-7 class of cab forward steam locomotives was the fourth class of the 4-8-8-2 locomotives purchased by Southern Pacific (SP). The locomotives were built by Baldwin Locomotive Works and shared many of the same characteristics of previous AC class locomotives.

Southern Pacific class AC-7
Type and origin
Power typeSteam
BuilderBaldwin Locomotive Works
Serial number61952-61963, 62038-62051
Build dateJanuary–August 1937
Gauge4 ft 8 12 in (1,435 mm) standard gauge
Driver dia.63 in (1,600 mm)
Adhesive weight514,800 lb (233,500 kg; 233.5 t)
Loco weight639,800 lb (290,200 kg; 290.2 t)
Boiler pressure250 psi (1.7 MPa)
Feedwater heater6SA Worthington
Cylinder size24 in × 32 in (610 mm × 813 mm) (bore × stroke)
Performance figures
Tractive effort124,300 lbf (553 kN)
OperatorsSouthern Pacific Railroad
Number in class26
Numbers4151 4176
First runFebruary 8, 1937
Retired1954 1958

The AC-7s were only slightly larger than their AC-6 predecessors, but they included larger tenders and a beveled cab front in contrast to the earlier classes' flat cab front. In the early 1940s, the majority of the class received larger cab windows of a design that would become standard with the AC-8 class.

In April 1937, locomotive number 4162 was pulled aside for a series of publicity photos at SP's Sacramento, California, shops. It was posed alongside the railroad's first locomotive, C. P. Huntington a diminutive 4-2-4T, especially when compared to 4162.

The AC-7 class locomotives were all removed from active service between 1954 and 1958, and they were all scrapped shortly after their removal from service. The first to be scrapped was 4155 on November 26, 1954, while the last was 4172 on April 24, 1959.


  • 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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