The Santa Clara Valley is a geologic trough in Northern California that extends 90 miles (140 km) south–southeast from San Francisco to Hollister. The longitudinal valley is bordered on the west by the Santa Cruz Mountains and on the east by the Diablo Range; the two coastal ranges meet south of Hollister. The San Francisco Bay borders the valley to the north, and fills much of the northern third of the valley. The valley floor is an alluvial plain that formed in the graben between the San Andreas Fault to the west and the Hayward and Calaveras faults to the east. Within the valley and surrounding the bay on three sides are the urban communities of San Mateo County, Santa Clara County, and Alameda County, while the narrow southern reaches of the valley extend into rural San Benito County to Hollister. In practical terms, the central portion of the Santa Clara Valley is often considered by itself, contained entirely within Santa Clara County.

The Santa Cruz Mountains are a mountain range in central and Northern California, United States, constituting a part of the Pacific Coast Ranges. They form a ridge down the San Francisco Peninsula, south of San Francisco. They separate the Pacific Ocean from the San Francisco Bay and the Santa Clara Valley, and continue south to the Central Coast, bordering Monterey Bay and ending at the Salinas Valley. The range passes through the counties of San Mateo, Santa Clara, and Santa Cruz, with the Pajaro River forming the southern boundary.