4 CA Counties Among Nation’s Biggest Population Losers. Here's Why

California is home to four counties ranked among the 10 nationwide that saw the greatest population declines last year,
according to recently published U.S. Census estimates.

That includes Los Angeles County, which saw a larger population loss than any other county in the United States between July 2024 and July 2025. Though the county lost around 54,000 residents, it's still the largest in the nation by far with an estimated population of 9,694,934, according to the Census Bureau.

Orange County ranked No. 5 on the list of top 10 counties by population decline: Its population shrank by 8,520 to a total estimated population of 3,149,507.

San Diego County came in at No. 6: Its population dropped by 5,294 to a total of 3,282,248.

Ventura County was ranked 10th: Its population fell by 2,580 to a total of 830,851.

Other large counties elsewhere in the U.S. also saw population declines, including Dallas County, New York City's Kings County and Miami-Dade County.

LA County's population loss equals a 0.55% change over a year. That's the greatest percent population loss of any of the nation's 10 largest counties, according to Census data.

For comparison, four of the nation's top 10 counties saw population gains. Among them was Riverside County, which saw a 0.63% increase in population, growing to 2,544,916.

Other large counties that grew are Houston's Harris County, Phoenix's Maricopa County and Chicago's Cook County.

An overall decline in immigration from outside the U.S. was among the factors: Net international migration into all American urban counties fell to about 932,000 — down from about two million the year before, according to the New York Times.

“The nation’s largest counties ... are often international migration hubs, gaining large numbers of international migrants and losing people that move to other parts of the country via domestic migration,” explained George M. Hayward, a Census Bureau demographer. "With fewer gains from international migration, these types of counties saw their population growth diminish or even turn into loss.”

At the same time, the nation’s largest counties — including Los Angeles — continued to lose residents to domestic migration, as more people moved to other parts of the country than moved in.

The counties with the largest growth in population were Houston's Harris County; Plano, Texas' Collin County; Phoenix's Maricopa County; Montgomery County outside of Houston; and Wake County, North Carolina's most populous county.

Looking at entire metro areas, which often include multiple counties, the Houston area saw the greatest population growth, adding 126,720 residents for a total population of 7,904,627.

The Dallas-Fort Worth metro area saw a similar number of people move in, bringing the area's population to 8,477,157.

The Atlanta, Phoenix and Charlotte, North Carolina areas rounded out the top 5 metro areas with the largest growth.

California is also home to three of the top 10 counties nationwide ranked by percent population decline. All counties on the list are small ones of around 80,000 people or fewer.

In California, that includes Del Norte County on the Oregon Border, which saw its population drop 2% to 26,410.

Tuolumne County, a mountainous area which includes Yosemite National Park, saw its population fall 1.9% to 53,160.

And Lassen County, in the far northeastern portion of the state, saw its population drop 1.7% to 28,117.

No Bay Area counties appeared on any of the Census Bureau's top 10 lists.

The figures are part of the Census Bureau’s annual population estimates program, which tracks demographic changes between the once-a-decade national census.

SEE ALSO:

• 16 Years Of Life Expectancy Separate LA County's Healthiest, Least Healthy Communities: Study
• These Are The Fastest-Growing Communities In CA, Census Data Show
• More People Are Moving Away From CA Than Any Other State: Report
• Californians Are Flocking To This Arizona City: Report
• CA Drops To World's Fifth-Largest Economy