Silicon Valley is a place and a state of mind, an area that had no distinctive identity three decades ago but that people all over the world today recognize and imitate. In the 1980s and ’90s, Silicon Valley emerged as the center of America’s computer industry, a place where creative minds develop products that large corporations never thought would sell. Its beginnings can be traced back to 1939, when William Hewlett and David Packard started their electronics firm in a Palo Alto garage, or perhaps even to 1891, when Stanford University was founded on the estate of a California governor and senator. Not every aspect of the computer business is centered here. Microsoft, routinely disparaged in every Palo Alto espresso shop and bar, is in Redmond, Wash., and the downsized IBM is in Armonk, N.Y., But Silicon Valley is where most of the giants and much of the creativity of the high-tech business—as well as many dot-coms—have been based.

How did Silicon Valley come to be where it is? One factor is Stanford, the students it attracts and produces, and its tradition of encouraging faculty members to pursue profit-making activity. Another key component is venture capital, widely available from innovation-minded old San Francisco money, dispensed mostly from nondescript office buildings on Sand Hill Road on the reclaimed flatlands along San Francisco Bay. A third ingredient is the presence of smart young innovators, attracted to the Valley’s lifestyle. Elite law and medical school graduates head to the prestigious, high-salary jobs of central cities. But techies are free to live in this pleasant, healthy environment. Sheltered by hills from coastal fogs and rains, Silicon Valley boasts a sunny climate with perceptible but gentle seasons, perfect for year-round outdoor sports. There may well be more jogging trails and bicycle paths here than anywhere else in the country. These communities were rustic but never poor, rural but not small-minded, country-like but still easily accessible to urban luxuries. People here were ahead of the rest of the nation in fighting for the environment, in favoring natural over processed foods, and in incorporating regular exercise into busy lives.

And the area has been quick to adapt to change. In the 1980s, in the face of threats from Japanese firms, Silicon Valley shifted to microprocessors and personal computers. In the 1990s, when PCs became a low-profit commodity business, Silicon Valley shifted to the Internet. Yahoo and Hotmail reportedly were conceived at Buck’s restaurant, the networking nexus in Woodside. When the Internet bubble burst in 2000, however, Silicon Valley fell on hard times. By one estimate, the area lost 220,000 jobs, nearly two-thirds of the 350,000 created during the dot-com boom. Stock prices plummeted and real estate prices did too, though they are still among the highest in the nation. The area actually lost population from 2000 to 2003. Billions of dollars in paper wealth disappeared, and technology exports from California fell. The question became whether Silicon Valley still had the ability to adapt. Before the 2008 recession, the Valley was in an upturn, with rising profits and a net gain of jobs, including increased research and investment in clean energy. But the recession took a toll in home values and start-up businesses. More than 140,000 jobs at Silicon Valley companies were lost in 2008, according to one local estimate.

The 14th Congressional District of California includes much of Silicon Valley, along with Menlo Park, Palo Alto, and most of Redwood City. Further south along El Camino Real are Mountain View and the several thousand employees of Google. Sunnyvale is the district’s largest city. There are some ultrawealthy enclaves here: Woodside, with its mansions dotting the hills, and Portola Valley and Los Altos Hills, with stark contemporary homes overlooking San Francisco Bay. Over the mountains, the district takes in the little town of Half Moon Bay, with its pumpkin farms rising over the ocean. Imposing redwoods grow within 5 miles of spectacular beaches. The 14th’s political heritage is progressive, with a sort of environmentalist, dovish, culturally liberal but entrepreneurial Republicanism, typified by former Reps. Pete McCloskey, Ed Zschau, and Tom Campbell, each of whom quit the House to run unsuccessfully for the Senate between 1982 and 2000. But this kind of Republican is now virtually extinct, and Silicon Valley has become Democratic. In 2008, Barack Obama won this district 73%-25%.