The 11 Most Expensive Counties In the U.S.

America’s most affluent zip codes live in a world of their own. Home to educated populations, healthy job markets, and a concentration of industries paying higher wages, the most expensive counties in the U.S. are very similar to each other yet entirely different. California, Colorado, Virginia, New York, and more states around the country host the most affluent counties in the U.S., and here’s a rundown of the ones you need to know. 

The Top 11 Richest Counties in the U.S.

1. Loudoun County, Virginia

Loudoun County has been topping lists as the wealthiest county in America since 2008. With a median household income of around $140,000, the county is as rich as they come. The origins of Loudoun's wealth dates back to the early 1960s when the Washington Dulles International Airport was constructed nearby. Soon, businesses followed prompted rapid growth, and eventually led to a boom in high-tech, well-paid jobs. Today, Loudoun still has a high demand for workers with advanced degrees, often in highly specialized industries. Therefore, residents are highly educated, frequently foreign-born, and make enough money to live in the most affluent county in the U.S. 

2. Santa Clara County, California

Santa Clara County is a part of the San Jose-Sunnyvale-Santa Clara metropolitan area known as Silicon Valley. 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. One in four workers here is employed in tech, information, professional, scientific, or management. In comparison, only 13.5 percent of all workers are employed in these sectors nationwide.

3. Marin County, California

Not too far from Santa Clara is Marin County, another one of the most affluent counties in the U.S. While it might be the smallest in the Bay Area, its riches are not to be underestimated. This is largely contributed by its sustainable environmental culture, and 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.

4. Los Alamos County, New Mexico

At first glance, Los Alamos doesn’t seem like a place with an affluent population. But in reality, it has some of the highest concentrations of millionaires per household in a small city in the U.S. The reason you ask? The Los Alamos National Laboratory is a large reason why. Top chemists, engineers, physicists, and other specialists have been pulling in hefty paychecks here since 1943, and with steady growth, this makes Los Alamos one of the most expensive counties in the U.S.

5. San Mateo County, California

Living in San Mateo is significantly more expensive than in the rest of the nation, but its job market is also one of the highest paying in California. What makes San Mateo one of the most expensive counties in the U.S. is the housing market. Real estate prices are about 200 percent higher than the national average in San Mateo and about 100 percent higher than the California average. But this county is simultaneously one of the best places to live in NorCal, so the benefits offset the costs.

6. Santa Barbara County, California

Paradise on the Pacific, the American Riviera, playground of the rich and famous, and where the sun shines 365 days a year—Santa Barbara has many nicknames. Even if you set aside all its desirable attributes, Santa Barbara snags a spot on any list of the wealthiest counties in America thanks to its impressive roster of celebrity residents, many of whom are household names. You can experience the area by planning a weekend getaway to Santa Barbara. 

7. Fairfax County, Virginia

Fairfax County is another Virginia entry on the list of most expensive counties in America. Like fellow D.C. suburb Prince William County, Fairfax is also a part of the Washington D.C. metro area, which happens to be home to one of the highest concentrations of millionaire households in America. 

As one of the wealthiest counties in America, Fairfax is home to ambitious and well-paid residents, a majority of whom are highly educated and foreign-born. In fact, the percentage of the educated and foreign-born population in Fairfax is almost double that of the national average.

8. City and County of San Francisco, California

San Francisco is considered California’s financial, commercial, and cultural center by many. Therefore, it’s natural that it’s one of the most affluent counties in the U.S. The vast majority of the income earned here comes from either investment or wages, and the housing expenses are also notoriously high.

9. Douglas County, Colorado

There's no doubt that incomes are high in Douglas County, but expenses are just as high. Housing, as usual, is the main culprit in making Douglas one of the most expensive counties in America. The affluent community costs about 40 percent more than what the average American pays.

10. Los Angeles County, California

The film and television industries are centered in L.A. the same way the tech industry is centered in the Bay Area. Therefore, with thousands of wealthy producers and talent residing in the area, L.A. easily makes the list of the top 11 richest counties in the U.S. Beyond that, Los Angeles County offers one of the best climates in the world, plenty of recreation opportunities, great schools, and world-class entertainment. 

11. Nassau County, New York

New York is known as the most populous metro area in the U.S. It’s also notorious for its high living wages. Nassau County, about a 46-minute drive from N.Y.C., is the most affluent of the state’s counties. With beautiful suburban neighborhoods, proximity to the city, and spectacular architecture, the Long Island “Gold Coast” remains one of the most expensive counties in the U.S.