Hetch Hetchy Railroad no. 6 is a standard gauge

Standard gauge

The standard gauge is a widely-used track gauge . Approximately 60% of the world's existing railway lines are built to this gauge...

 three truck Shay locomotive

Shay locomotive

The Shay locomotive was the most widely used geared steam locomotive. The locomotives were built to the patents of Ephraim Shay, who has been credited with the popularization of the concept of a geared steam locomotive...

 built for the Hetch Hetchy Railroad

Hetch Hetchy Railroad

The Hetch Hetchy Railroad was a standard gauge Class III railroad constructed by the City of San Francisco to support the construction and expansion of the O'Shaughnessy Dam across Hetch Hetchy Valley....

 by Lima Locomotive Works

Lima Locomotive Works

Lima Locomotive Works was an American firm that manufactured railroad locomotives from the 1870s through the 1950s. The company took the most distinctive part of its name from its main shops location in Lima, Ohio. The shops were located between the Baltimore & Ohio's Cincinnati-Toledo main line...

 in 1921.

Although it operated as a common carrier

Common carrier

A common carrier in common-law countries is a person or company that transports goods or people for any person or company and that is responsible for any possible loss of the goods during transport...

, the Hetch Hetchy Railroad was built by the City of San Francisco to build the O'Shaughnessy Dam

O'Shaughnessy Dam

The O'Shaughnessy Dam is a curved gravity dam on the Tuolumne River in the Hetch Hetchy Valley of California's Sierra Nevada. The dam is located in Yosemite National Park, and creates the Hetch Hetchy Reservoir. It is named for former San Francisco chief engineer and the original chief engineer of...

 across Hetch Hetchy Valley

Hetch Hetchy Valley

Hetch Hetchy Valley is a glacial valley in Yosemite National Park in California. It is currently completely flooded by O'Shaughnessy Dam, forming the Hetch Hetchy Reservoir. The Tuolumne River fills the reservoir. Upstream from the valley lies the Grand Canyon of the Tuolumne. The reservoir...

 as part of the city's water supply. The dam was completed in 1923 and the railroad scaled back operations, selling some of its equipment, including #6, which was sold to Pickering Lumber Corporation in Standard, California

Standard, California

Standard is an unincorporated community in Tuolumne County, California, United States that lies east-southeast of Sonora. Its post office, opened in 1910, is assigned ZIP code 95373. Standard was established as a company town for the Standard Lumber Company....

. The locomotive served Pickering's logging operations until 1958 when it was retired.

The railroad operated four Shays at different times. Number 6 was by far the largest, the only three truck Shay of the lot and weighing more than twice as much as the others.

It is in a small collection of railroad equipment owned by the National Park Service

National Park Service

The National Park Service is the U.S. federal agency that manages all national parks, many national monuments, and other conservation and historical properties with various title designations...

 near El Portal, California

El Portal, California

El Portal is a census-designated place in Mariposa County, California. It is located west-southwest of Yosemite Village, at an elevation of 1939 feet . The population was 474 at the 2010 census....

. Number 6 was added to the National Register of Historic Places

National Register of Historic Places

The National Register of Historic Places is the United States government's official list of districts, sites, buildings, structures, and objects deemed worthy of preservation...

in 1978 as Hetch Hetchy Railroad Engine No.6.