Southern Pacific Railroad

Southern Pacific Railroad

The Southern Pacific Transportation Company , earlier Southern Pacific Railroad and Southern Pacific Company, and usually simply called the Southern Pacific or Espee, was an American railroad....

's AC-4 class of steam locomotive

Steam locomotive

A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...

s was the first class of cab forward

Cab forward

The term cab forward refers to various rail and road vehicle designs which place the driver's compartment substantially farther towards the front than is common practice.- Rail locomotives :...

 locomotives built with the 4-8-8-2

4-8-8-2

Under the Whyte notation for the classification of steam locomotives, a 4-8-8-2 is a locomotive with four leading wheels, two sets of eight driving wheels, and a two-wheel trailing truck.Other equivalent classifications are:...

 wheel arrangement. They were designed as an improvement upon the railroad's existing MC class 2-8-8-2

2-8-8-2

.A 2-8-8-2, in the Whyte notation for describing steam locomotive wheel arrangements, is an articulated locomotive with a two-wheel leading truck, two sets of eight driving wheels, and a two-wheel trailing truck. The equivalent UIC classification is, refined to Mallet locomotives, D1...

 locomotives having a larger firebox.

The AC-4s were built in August through October 1928 by Baldwin Locomotive Works

Baldwin Locomotive Works

The Baldwin Locomotive Works was an American builder of railroad locomotives. It was located in Philadelphia, Pennsylvania, originally, and later in nearby Eddystone, Pennsylvania. Although the company was very successful as a producer of steam locomotives, its transition to the production of...

. As delivered, they produced 112760 lbf (501.6 kN) of tractive effort

Tractive effort

As used in mechanical engineering, the term tractive force is the pulling or pushing force exerted by a vehicle on another vehicle or object. The term tractive effort is synonymous with tractive force, and is often used in railway engineering to describe the pulling or pushing capability of a...

; after a January 1931 rebuild, this class was capable of 116900 lbf (520 kN) of tractive effort.

All ten of the AC-4s were removed from active service between 1953 and 1955 and scrapped by June 1955.