Silicon Valley is in the southern part of the San Francisco Bay Area in Northern California, United States. The region is home to many of the world’s largest technology companies including Apple, Google, Facebook, HP, Intel, Cisco, eBay, Adobe, Agilent, Oracle, Yahoo, Netflix, and EA.
The term originally referred to the region’s large number of silicon chip innovators and manufacturers, but eventually came to refer to all the high-tech businesses in the area; it is now generally used as a metonym for the American high-tech sector of which you can learn more by checking this industrial automation specialist Melbourne website.
Despite the development of other high-tech economic centers throughout the United States and the world, Silicon Valley continues to be the leading hub for high-tech innovation and development, accounting for 1/3 of all of the venture capital investment in the United States. Source: Wikipedia
I once came across this awesome map at SFO of Silicon Valley tech-companies distributed across the valley. And here she is:
High-tech companies in Silicon Valley
The full list of companies can be found here: