Elaine White, a real-estate agent and native of neighbouring Redwood City, has watched the tech boom shape the region.
"Because of how big Facebook has gotten, and Google, we've kind of become this concept of the company town, where so many people work for these Silicon Valley companies," she said.
In Atherton, the cheapest house on the market is currently listed for $US2.5 million, according to real estate marketplace Zillow.com. Numerous tech billionaires have called the town home, including Google's Eric Schmidt, Facebook's Sheryl Sandberg and Microsoft's late co-founder Paul Allen, whose former residence there was sold last week for more than $US35 million. Golden State Warriors athlete Stephen Curry bought an Atherton estate last year for $US31 million.
A street view and satellite view of the same area in Atherton, California.
Coast to coast
In second place for the second straight year is Scarsdale, New York, less than 25 miles (40km) outside Manhattan, with an average $US452,000 in annual household income. Also making the top 10 are a town near Denver, two northern suburbs of Chicago, and a wealthy enclave in Dallas, Texas.
In general, the East and West Coasts dominate the top-100 list. California takes up 23 places, while the tri-state area of New York, Connecticut and New Jersey accounts for 32 (although that's down from 36 last year). Middle America is slowly gaining some ground. States including Illinois and Minnesota added one new listing in this year's index, while Texas gained two (Lucas at No. 73, and Alamo Heights at No. 75).
Altogether, 16 states are represented on the list, the same number as in previous years - suggesting that the concentration of wealth in certain regions remains largely unchanged over time. Also, the richest communities continue to get richer. This year, in order to make the top 100, a neighbourhood needed an average household income of $US220,000 - up from $US209,000 last year.
Bloomberg evaluated inflation-adjusted household data for all US locations with a minimum of 2000 households (as defined by the Census), and ranked them based on average household income. Almost 6300 communities met the criteria, which includes about 75 per cent of total households in the US.