What’s the wealthiest county in California? Hint: It’s not LA or San Francisco
More than half of the wealthiest counties in California can be found in a single region, according to SmartAsset.
Northern California is also home to a significant number of the state’s poorest spots, the personal financial website found.
SmartAsset recently highlighted the places across the United States with the “greatest amounts of wealth” in 2025, based on investment income, median income and median home value.
Residents in California’s richest county — San Mateo County — enjoy a median household income of $156,000 per year, SmartAsset said
That’s nearly $60,000 more than the statewide median household income of $96,334 a year, according to data from the U.S. Census Bureau.
In contrast, households in California’s poorest county, Modoc County, make about $40,000 less per year than the California median income amount.
California ranks sixth in the nation in terms of annual household earnings, Census data show, trailing Massachusetts and Hawaii.
What’s the No. 1 wealthiest county in California?
According to SmartAsset, San Mateo County ranked No. 1 in California in terms of overall wealth in 2025.
It ranked No. 4 in terms of the wealthiest counties in the United States, , the personal finance website said, following Pitkin County in Colorado and Nantucket County in Massachusetts.
Part of the Santa Clara Valley, San Mateo County had an estimated population of 742,893 residents as of July 2024, according to the Census Bureau.
“Innovation thrives here in industries including bioscience, computer software, green technology, hospitality, financial management, health care, education and transportation,” San Mateo County said on its website, noting the county’s proximity to Silicon Valley.
San Mateo County had a median home value of $1,543,376, according to SmartAsset.
In comparison, the average California home value was $796,255 as of Friday, May 30, according to real estate website Zillow.
On average, San Mateo County residents make $146,004 in annual investment income, SmartAsset said.
Where are the richest counties in California?
According to SmartAsset, seven of California’s 10 wealthiest counties were in the Bay Area in 2025, while one was on the Central Coast and two were in Southern California.
These were the 10 richest counties in California in 2025, according to Smart Asset:
No. 1: San Mateo County
Median income: $156,000
Median home value: $1,543,376
No. 2: Santa Clara County
Median income: $159,674
Median home value: $1,501,824
No. 3: Marin County
Median income: $142,785
Median home value: $1,438,437
No. 4: Contra Costa County
Median income: $125,727
Median home value: $1,438,437
No. 5: Alameda County
Median income: $126,240
Median home value: $1,080,745
No. 6: Santa Cruz County
Median income: $109,266
Median home value: $1,138,101
No. 7: Orange County
Median income: $113,702
Median home value: $1,003,290
No. 8: Solano County
Median income: $99,994
Median home value: $580,106
No. 9: Napa County
Median income: $108,970
Median home value: $873,494
No. 10: Santa Barbara County
Median income: $95,977
Median home value: $885,640
What are the poorest counties in California?
About 12% of California’s population lives in poverty, according to the Census Bureau.
According to SmartAsset, all but two of the 10 poorest California counties can be found in the northern part of the state.
These were the 10 poorest counties in California in 2025 based on overall wealth, according to the site:
No. 1: Modoc County
Median income: $56,648
Median home value: $173,763
No. 2: Trinity County
- Median income: $53,498
- Median home value: $308,921
No. 3: Siskiyou County
- Median income: $55,499
- Median home value: $286,105
No. 4: Lassen County
- Median income: $64,395
- Median home value: $224,424
No. 5: Imperial County
- Median income: $56,393
- Median home value: $309,794
No. 6: Sierra County
- Median income: $60,000
- Median home value: $315,832
No. 7: Lake County
- Median income: $58,738
- Median home value: $328,199
No. 8: Tehama County
- Median income: $61,834
- Median home value: $312,295
No. 9: Del Norte County
- Median income: $66,780
- Median home value: $335,634
No. 10: Mariposa County
- Median income: $65,378
- Median home value: $395,722
How did SmartAsset come up with its rankings?
To rank the wealthiest and poorest counties in California, SmartAsset said it compared all U.S. counties across three metrics: investment income, property value and median income.
The personal finance website calculating the investment index for each county by “evenly weighing the ordinary dividends, qualified dividends and net capital gains,” it said, then calculated the median home value and the median income for each one.
SmartAsset calculated a wealth index for all U.S. counties and “ranked them accordingly to provide a holistic view of what areas of the U.S. are accumulating the most wealth,”
SmartAsset used data from sources including real estate website Zillow, the Internal Revenue Service’s Statistics of Income Tax Statistics and the U.S. Census Bureau’s 2023 American Community Survey.
This story was originally published June 2, 2025 at 5:00 AM.
