From the San Francisco Chronicle — It’s an environmental conflict that has been coursing through California for more than a century: the unrelenting thirst of San Francisco versus the pristine beauty of nature.

After years of debate, O’Shaughnessy Dam opened in 1923, holding back the Tuolumne River and flooding Hetch Hetch Valley, a Sierra gem compared in its grandeur to nearby Yosemite Valley. As final construction continued into the 1930s, San Franciscans began tasting water piped directly from Hetch Hetchy Reservoir to their homes.

These photos were recently found in The Chronicle’s archive, and many haven’t been published in decades.