Atherton, Calif., is America's richest place for the third year in a row. Its residents made an average of $450,696 in 2017, a $7,293 increase from the prior year, according to the annual Bloomberg Richest Places index.

Medina, west of Minneapolis, made its debut in the top 100.

Billionaires who have called Atherton home include Google's Eric Schmidt and Facebook's Sheryl Sandberg. Both Google and Facebook have headquarters within 10 miles of Atherton, which is nestled inside the nation's tech hub dubbed Silicon Valley. Stanford University is just 2 miles down the road from the town.

Atherton Mayor Bill Widmer said the tree-lined streets and lot sizes of at least 1 acre offer the residents privacy.

"We value a semi-rural environment," said Widmer, who moved to Atherton in 1996. "There are few sidewalks and many places don't have streetlights."

Scarsdale, N.Y., a wealthy suburb north of Manhattan, moved up to the No. 2 spot on this year's list as its residents enjoyed a $30,000 increase, on average, in annual household income from the prior year, pushing Cherry Hills Village, Colo., to the No. 3 spot. Top school districts are one reason why residents choose to live there.

"We moved here as many did because of the outstanding school system," said Scarsdale Mayor Dan Hochvert, a 40-year resident. "That is one of the primary drivers."

Accessibility to a city center is also a key characteristic of all three. Just as Atherton is accessible to San Francisco and Scarsdale is a train's ride away from New York City, Cherry Hills Village is a 15- to 20-minute drive to both downtown Denver and the city's tech center.

"It happens to be located kind of beautifully," said Steve Blank, a managing broker at Sotheby's International Realty in Denver.

Big wigs living in Cherry Hills Village include Super Bowl-winning quarterback Peyton Manning and Denver Broncos General Manager John Elway.

More than half of the top 100 richest places in America were either in the tri-state area — New York, New Jersey and Connecticut — or California. Still, a number of Midwest and Southwest areas made the cut and a handful even are in the top 20.

The bar to make it among the top 100 places was raised to $209,000 in annual income from $198,000 a year earlier. Four places made their top 100 debut this year including two in California: Tamalpais-Homestead Valley in Marin County and beach city Del Mar; Jericho in New York's Long Island and Medina.

Wealth is further concentrated specifically in six counties: Westchester, Bergen and Fairfield counties outside of Manhattan, Cook County of Chicago, Los Angeles County and Montgomery County in Maryland, bordering Washington, D.C.

Rumson, a wealthy corner of Monmouth County, N.J., ascended 19 spots into the top 20. Bernardsville, another New Jersey town, jumped 31 spots and the average income increased $30,000 to $231,336.

Florida moved down the exclusivity list. The same four places in Florida made the top 100 list but three of them ranked lower this year versus last. Indian River Shores, near Vero Beach, dropped out of the top 50 as the average annual income decreased by $20,000.