Granite Rock Co. 10

Granite Rock Company No. 10 is a preserved S100 class steam locomotive built in 1942 by H.K. Porter for the United States Transportation Corps.

Army service
No. 10 was built in Pittsburgh, Pennsylvania, by H.K. Porter in 1942, for the United States Transportation Corps. (USATC), originally No. 5001, it served in the Army depot in Tracy, California.

Industrial service
After World War II, in 1947, No. 5001 was sold to the Granite Rock Company of Watsonville, California and given the number 10. The locomotive worked at the company's A.R. Wilson quarry in Aromas, California until the 1950s, when it was replaced by diesel locomotives and taken out of service.

Preservation
No. 10 stayed in Granite Rock's yards, until Bruce Woolpert the president and CEO, started a restoration effort in 1988 The work was undertaken at the shops of the California State Railroad Museum. The company donated No. 10 to the museum in 1997. The restoration work included a new boiler built by the Dixon Boilerworks, in Los Angeles. The locomotive was fully restored to operating condition by May 1997, and became the principle motive power of the museum's Sacramento Southern Railroad excursion railroad.

On August 29, 1997, No. 10 was operated by an all-female crew to mark the anniversary of the ratification of the 19th. Amendment.

In 2010, No.10 was loaned to the Niles Canyon Railway for their steam festival. The following year, No. 10 was taken out of service for extensive boiler repairs, before returning in April 11, 2015.

As of 2024, No. 10 is still out of order as the museum is fixing some cylinder issues and reworking the valve bushings.