

But in reality, it has some of the highest concentrations of millionaires per household in a small city in the U.S. Upon first glance, Los Alamos doesn’t seem like a place with an affluent population. This is largely contributed by its sustainable environmental culture, strategic location between Napa and San Francisco-which makes it an amazing weekend getaway spot -a high-paying job market, and a large portion of a retired population with significant wealth. While it might be the smallest in the Bay Area, its riches are not to be underestimated. Not too far from Santa Clara is Marin County, another one of the most affluent counties in the U.S. In comparison, only 13.5 percent of all workers are employed in these sectors nationwide. One in four workers here is employed in tech, information, professional, scientific, or management. And what would a list of the most expensive counties in America be without Silicon Valley? Since many of the recognized innovative companies are headquartered here, it contributes most to making Santa Clara one of the most expensive counties in the U.S.

Santa Clara County is a part of the San Jose-Sunnyvale-Santa Clara metropolitan area known as Silicon Valley. Therefore, residents are highly educated, frequently foreign-born, and make enough money to live in the most affluent county in the U.S. Today, Loudoun still has a high demand for workers with advanced degrees, often in highly specialized industries. Soon, businesses followed, prompted rapid growth, and eventually led to a boom in high-tech, well-paid jobs. The origins of Loudoun's wealth dates back to the early 1960s when the Washington Dulles International Airport was constructed nearby.

With a median household income of around $140,000, the county is as rich as they come. Loudoun County has been topping lists as the wealthiest county in America since 2008.
