Carleton Watkins became nationally renowned for the spectacular series of mammoth-plate photographs he made of Yosemite Valley in 1861. On that trip, and on his seven subsequent visits to the valley, Watkins brought with him an immense, custom-made camera that was capable of exposing 18-by-22-inch glass plates. Though unwieldy, particularly because they had to be sensitized and processed in the field, these mammoth-plate negatives allowed Watkins to capture the vastness and grandeur of Yosemite in exceptional detail.

In the 19th century, Yosemite was often seen as a foil for San Francisco, an Edenic alternative to the dirty and congested city. Watkins’s majestic pictures helped convince Abraham Lincoln to sign the Yosemite Bill in 1864, making the valley the first area set aside by the government for protection from development.