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 type Steam Builder Baldwin Locomotive Works Serial number 36490-36493, 36524-36527, 36614-36616, 36634 Build date April–May 1911
Specifications Configuration: ​  • Whyte 2-8-8-2 Gauge 4 ft 8+1⁄2 in (1,435 mm) standard gauge Driver dia. 57 in (1,448 mm) Adhesive weight 398,500 lb (180,800 kg) Loco weight 432,600 lb (196,200 kg) Boiler pressure 200 psi (1.4 MPa) High-pressure cylinder 26 in × 30 in (660 mm × 762 mm) Low-pressure cylinder 40 in × 30 in (1,016 mm × 762 mm)
Performance figures Tractive effort 85,040 lbf (378.28 kN)
Career Operators Southern Pacific Railroad Class MC-4 Numbers 4017 – 4028 First run July 21, 1911 Retired 1947 – 1948 Disposition scrapped

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.