Southern Pacific 18

18 was originally built in 1911 for the Nevada–California–Oregon Railway and was sold to Southern Pacific in 1926. No. 18 worked the rest of its career on the Southern Pacific narrow-gauge. The locomotive, along with sisters Nos. 8 and 9, were nicknamed "The Desert Princess" for serving the desert areas of Nevada and California.

In 1954, a new narrow-gauge General Electric diesel locomotive was purchased as Southern Pacific No. 1 to replace Nos. 8 and 18, resulting in the two steam locomotives retiring soon after the arrival of No. 1. No. 8 was donated to the City of Sparks, Nevada, while No. 18 was donated to the City of Independence, California.

No. 9 was the last Southern Pacific narrow-gauge steam locomotive to retire and pull a Southern Pacific narrow-gauge passenger train, with the last day of steam operation on the narrow-gauge line being August 25, 1959 and was retired a year later.

The locomotive was preserved, along with No. 8 and E9 Unit No. 18, was restored for operating condition between 2009 and July 2017 on a short stretch of track in a public park in Independence, California. Then, in early November 2018, No. 18 was leased to the Durango and Silverton Narrow Gauge Railroad in Durango, Colorado, to train the crew on an oil burner, as the D&SNG is restoring K-37 No. 493 to operational condition while also converting the locomotive from burning coal to burning fuel oil.

On April 9, 2019, while the locomotive was working a spring excursion, a piston ring broke, creating a hole in the right-side cylinder head. The failure of the piston ring occurred on the grades between Hermosa and Rockwood. The four passenger cars, along with 100 passengers on board, were hauled back to Durango. The next day, No. 18 was hauled back to Durango for repairs. The cause of the piston ring failure is unknown. On July 22, 2019, the engine returned to service. No. 18 returned home to the Eastern California Museum in October 2019.