The San Francisco Public Utilities Commission (PUC) digital collection is based at the San Francisco Public Library. It includes over 300 images, spanning 1887 to 1968, of significant events and projects such as the building of the Hetch Hetchy Railroad and O'Shaughnessey Dam, the construction of the Golden Gate International Exposition on Treasure Island, and so on. These fascinating historic industrial photographs document the pipelines, tunnels, reservoirs, dams, powerhouses, and pumping stations that the PUC has built and maintained in order "to provide water, sewerage and municipal services to the City and County of San Francisco." Visitors can click on the link provided here to view the images, or perform their own detailed search across the entire collection. The views of the Calaveras Dam are quite dramatic and there are many photos documenting the Golden Gate International Exposition as well.