Yosemite National Park, located in the central part of California’s Sierra Nevada mountains, is a glacially carved landscape filled with iconic rock formations such as Cathedral Peak, El Capitan, and Half Dome. Igneous rocks, consisting primarily of variations of granite, granodiorite, and tonalite, make up the majority of the bedrock geology and their overall strength supports the spectacular cliffs and domes of Yosemite Valley that draw many visitors to the park. These same sheer cliffs also are the source areas for frequent rock falls, which, in addition to being the primary mechanism for cliff formation, can also pose a hazard to visitors and infrastructure located below. To obtain rock strength parameters for use in assessing rock-fall potential in Yosemite National Park, we conducted a comprehensive rock mechanics laboratory testing program on a set of granitic rocks that form many of the cliffs in Yosemite Valley.