One day in early July 1861, Carleton Watkins set up his cumbersome camera along the Merced River and aimed it eastward up the Yosemite Valley toward Tasayac, or Half Dome, a peak that towered a half mile above the valley floor. In that instant, Watkins captured for the first time what millions of park visitors would subsequently shoot from that same vantage point.

The awed reports of the first visitors to Yosemite convinced Watkins to venture the two hundred miles from San Francisco, trundling by pack mule nearly a ton of gear, including an entire portable photographic studio. This included his mammoth camera, nearly three feet square and built to a size never before used in the western landscape, but necessary to produce negatives (and positives) that would measure up to the magnitude of the scenery. The physical challenges of fieldwork and the technical limitations of the relatively new art of photography were imperceptible in Watkins's exposures, which were as breathlessly still, immaculate, and perfectly composed as the place itself. Watkins's thirty large-format images were exhibited in New York in 1862. They proved to incredulous easterners, as only photography could, that the marvels of Yosemite were a fact and motivated Congress in 1864 to set aside and protect the Valley forever.

Without crossing the continent . . . we are able to step . . . from our study into the wonders of the wondrous valley, and gaze at our leisure on its amazing features.
-The Philadelphia Photographer, 1866