Decades before Ansel Adams ever saw Yosemite’s jagged peaks, Carleton Watkins packed his mammoth plate camera, tripods and a makeshift tent darkroom on mules and ventured into the remote California valley.

At the journey’s end, Watkins had 130 negatives that offered the first printed images of Yosemite’s towering masses, glacial geology and jaw-dropping expanse.

The images, including Watkins’ intimate view of Cathedral Rock, floored the growing nation’s power brokers. John Conness, a U.S. Senator from California, owned a set of the prints and became an evangelist for the work.

On June 30, 1864, President Abraham Lincoln signed into law the Yosemite Grant Act, laying the foundation for the National Park System, which now protects some 84 million acres of land.