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Which counties are included in Silicon Valley?

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Map of Silicon Valley with colored markers showing tech locations: blue historically important offices, green HQs, orange offices, and purple clusters across the Bay Area. — Silicon Valley Silicon Valley highlighting key historic tech offices, major tech headquarters, and offices with headquarters elsewhere.

Silicon Valley is an industrial region located around the southern shores of the San Francisco Bay in California. It encompasses the following counties:

Santa Clara County: Includes the northwestern portion of the county, extending inland as far as San Jose.1
Alameda County: Includes the southern bay regions of the county.1
San Mateo County: Includes the southern bay regions of the county.1

The region serves as a global center for electronics and computer industries, with its intellectual hub centered in Palo Alto, home to Stanford University.1