Last updated: November 7, 2021
Named for the chief engineer, the O’Shaughnessy Dam was completed in 1938 and is 430-feet tall. Today the 117-billion-gallon reservoir supplies drinking water to about 2.5 million San Francisco Bay Area residents and industrial users. It also supplies hydro-electric power generated by two plants downstream. The reservoir is eight miles long and the largest single body of water in Yosemite.