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Which counties in California are losing population?

36 of the 58 counties in California had fewer residents in 2025 than in 2020. Lassen County lost the largest share, down 13.1% (−4,232 people). Los Angeles County lost the most residents (−301,576).

Of the 36 counties that lost residents between 2020 and 2025, the largest factor was natural change (more deaths than births) in 11 and net domestic migration (more residents moving to other U.S. counties than arriving) in 25 (Census Bureau components of population change).

Data as of 2025 · updated

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All 36 California counties that lost residents

Counties losing population in California
RankCountyChange 2020–25Residents lost 2020–25Residents 2025Largest factor 2020–25
1Lassen County−13.1%−4,23228,117Domestic migration (−4,528)
2Alpine County−11.6%−1371,043Natural change (−73)
3Plumas County−5.9%−1,16218,583Domestic migration (−723)
4San Francisco County−5.6%−49,060826,079Domestic migration (−79,909)
5Mono County−5.4%−71712,505Domestic migration (−1,254)
6Santa Cruz County−4.7%−12,906258,852Domestic migration (−15,429)
7Siskiyou County−4.5%−1,97042,013Natural change (−1,351)
8Del Norte County−4.4%−1,20926,410Domestic migration (−647)
9Inyo County−4.4%−83118,158Domestic migration (−467)
10Tuolumne County−4.0%−2,20953,160Natural change (−1,608)
11Sierra County−4.0%−1283,098Natural change (−124)
12Mendocino County−3.5%−3,22688,122Domestic migration (−3,354)
13Humboldt County−3.4%−4,651131,647Domestic migration (−3,162)
14Napa County−3.3%−4,532132,949Domestic migration (−5,824)
15Los Angeles County−3.0%−301,5769,694,934Domestic migration (−667,953)
16Marin County−2.9%−7,643253,694Domestic migration (−14,290)
17Modoc County−2.9%−2538,426Natural change (−306)
18Alameda County−2.6%−43,8591,636,630Domestic migration (−141,108)
19Glenn County−2.6%−74828,141Domestic migration (−1,202)
20San Mateo County−2.5%−19,071743,568Domestic migration (−64,201)
21Trinity County−2.4%−37915,720Natural change (−376)
22Tehama County−1.7%−1,09564,665Domestic migration (−931)
23Monterey County−1.5%−6,764433,729Domestic migration (−26,520)
24Ventura County−1.5%−12,942830,851Domestic migration (−30,881)
25Santa Barbara County−1.4%−6,260442,065Domestic migration (−23,912)
26Mariposa County−1.2%−21216,918Natural change (−403)
27Orange County−1.2%−36,6603,149,507Domestic migration (−144,371)
28Santa Clara County−0.9%−16,9581,914,391Domestic migration (−168,614)
29Sutter County−0.7%−67698,787Domestic migration (−4,869)
30Lake County−0.6%−43667,772Natural change (−1,544)
31San Diego County−0.6%−18,8623,282,248Domestic migration (−133,070)
32Butte County−0.5%−993209,211Natural change (−1,855)
33Sonoma County−0.4%−2,070486,444Domestic migration (−7,935)
34Nevada County−0.4%−369101,911Natural change (−1,933)
35Shasta County−0.3%−543181,648Natural change (−3,355)
36Colusa County−0.1%−2221,836Domestic migration (−536)

How this is ranked

Counties whose Census Bureau resident population estimate for July 1, 2025 is lower than for July 1, 2020, steepest percentage decline first. The largest factor is the most negative of natural change (births minus deaths), net domestic migration and net international migration over the same years (Census Bureau components of population change). Counties with fewer than 1,000 residents, or without a figure for the same period as the others, are left out, as on every ranking.

Source: U.S. Census Bureau, Population Estimates Program (Vintage 2025). Figures come from public federal statistics and are informational only, not investment advice. Check the source before relying on a number. Methodology: how ranks and figures are built. More on every layer: data sources and licences.

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Questions

Which county in California is losing population fastest?

Lassen County: down 13.1% between 2020 and 2025, to 28,117 residents (−4,232 people; Census Bureau population estimates). Next: Alpine County (−11.6%) and Plumas County (−5.9%).

How many counties in California are losing population?

36 of the 58 counties in California had fewer residents in 2025 than in 2020; the other 22 grew or held steady.

Why are counties in California losing population?

Of the 36 counties that lost residents between 2020 and 2025, the largest factor was natural change (more deaths than births) in 11 and net domestic migration (more residents moving to other U.S. counties than arriving) in 25 (Census Bureau components of population change).

More county rankings for California

Counties losing population in other states

Across the U.S.