In 1930, Western Pacific's subsidiary Sacramento Northern began serving its largest customer: the United States Steel mill in Pittsburg, CA. Dedicated trains of raw materials and coil steel were shipped via the WP and SN to Pittsburg for further processing. The mill remains in operation today, now operated as a joint venture by USS and Korean steel maker POSCO, and is still served by WP successor Union Pacific.

Starting in the 1970's, cars within the mill were switched by a small fleet of diesel locomotives built by the Baldwin Company. Baldwin had been the largest builder of steam locomotives in the US, but the change to diesels had left the company out in the cold. It tried to compete, but its products were never as popular as industry leader Electro-Motive Division. Still, its locomotives did prove durable and many shortlines and industrial railroads kept them running long after the company closed its railroad division in 1956.

USS 20 was built in 1951 for Oliver Mining, an iron ore producer in Michigan that was part of the USSteel company. By the mid-1970's, it was transferred to Pittsburg where it switched cars brought in by the SN and the Santa Fe Railway. Baldwin locomotives had become rare by then and USSteel's fleet of 3 became well-known among local fans. At some point, the 20 received remote control gear, allowing it to be operated by an engineer standing on the ground using a special controller. It was retired in the late 1980's and purchased by the FRRS, one of the few locomotives at the museum once owned by a customer of the WP system.

model:

builder:

built:

builder number:

prime mover:

horsepower:

operating weight:

length:

max. speed:

S12

Baldwin-Lima-Hamilton

June 1951

75053

606A - 6 cylinder

1200

lbs.

.