Methodology: 

To identify the richest county in each state, 24/7 Wall St. reviewed median annual household incomes for each U.S. county using 5-year estimates from the U.S. Census Bureau’s 2018 American Community Survey. We only considered counties with income estimates with a maximum 10% margin of error. 

We also reviewed in each county the percentage of adults who have earned a bachelor’s degree or higher, poverty rate, and median home value from the ACS. Unemployment rates for October 2019 are from the Bureau of Labor Statistics and are not seasonally adjusted. 

County equivalents, such as parishes in Louisiana and boroughs in Alaska, were included in our analysis. Alaskan Census areas, however, which are sparsely populated andare under the purview of the state government, were excluded.