From Wikipedia: “Alfred A. Hart (1816–1908) was a 19th-century American photographer for the Central Pacific Railroad. Hart was the official photographer of the western half of the first transcontinental railroad, for which he took 364 historic stereoviews of the railroad construction in the 1860s. Hart sold his negatives to Carleton Watkins, who continued to publish the CPRR stereoviews in the 1870s.”

A full version of a Book about his railroad photographs is online.

A Monument in the shape of a stereoscopic camera was installed in Sacremento, CA