Silicon Valley is in the southern part of the San Francisco Bay Area in Northern California. It is called Silicon Valley because the industry uses silicon to make semiconductor chips. It has been called Silicon Valley for 41 years, starting 1971. Silicon Valley is important because it's the the most productive high-tech area, leading the U.S. in experimenting and developing technolgy.
Bill Gates built his first computer in Albuquerque.
http://en.wikipedia.org/wiki/Silicon_Valley
http://www.netvalley.com/silicon_valley_history.html
http://en.wikipedia.org/wiki/Bill_Gates#Microsoft