Giant redwood trees growing in the Muir Wood near Nappa Valley to the north of San Francisco.

Giant redwood trees growing in the Muir Wood near Nappa Valley to the north of San Francisco.

River flowing through an area known as the Tioga Pass in the Yosemite National Park (Sierra Nevada Mountains).

River flowing through an area known as the Tioga Pass in the Yosemite National Park (Sierra Nevada Mountains).

Joshua Tree, Yucca brevifolia, growing in the Nevada Desert.

Joshua Tree, Yucca brevifolia, growing in the Nevada Desert.