5 Wealthiest Counties in the US

4. San Mateo County

Median Household Income: $128,091

San Mateo County ranks as the 4th wealthiest county in the United States with a median household income of $128,091. The California county covers much of the San Francisco Peninsula and is headquarters to several companies such as Visa Inc. (NYSE:V). Given the substantial median household income in the county, real estate values in San Mateo County rank among the highest in the United States.