The top 10 counties with the highest number of millionaire residents are:
1. Los Angeles County, California: With 268,136 millionaire households, Los Angeles County has the largest number of millionaires among the counties in the U.S. The County has 23 % of California's millionaire households and 3 % of those in the country.
2. Cook County, Illinois: Cook County, which includes Chicago, has 171,118 millionaire households forming 40 % of such households in Illinois and 2 % in the nation.
3. Orange County, California: Orange County consists of 10 % of California's millionaire households with 116,157 millionaire households. It forms 1 % of the nation's millionaire households.
4. Maricopa County, Arizona: With 113,414 households, Maricopa County has the 4th largest number of millionaire households in USA. This makes 62 % of Arizona's total millionaire households and 1 % of the nation's.
5. San Diego County, California: The fifth county in the U.S. and the 3rd in the State with the most number of millionaire households, San Diego has 102,138 millionaire households that make up 9 % of such households in California. It also accounts for 1 % of the total millionaire households in the country.