Cook County saw little population change in 2025 due to reduced international immigration, new U.S. census numbers show, but Kendall County bucked that nationwide trend with the greatest percentage growth among all counties in Illinois.
Cook County grew by an estimated 5,834 people, or 0.1%, from July 1, 2024, to July 1, 2025.
But the southwest suburbs showed continued signs of growth. Kendall County grew by 1.6%, or almost 14,000 people, while Will County had the greatest numeric increase, with almost 15,000 people, or 0.5%.
Kendall County Administrator Christina Burns said the county has returned to growth levels comparable to before the recession of 2008, when Kendall was the fastest-growing county in the country.
“When families come to Kendall County, it’s a family looking to settle down and be part of a growing community,” she said.
The mayor of Yorkville, John Purcell, said the town added a couple of hundred new homes last year, down from a peak of maybe twice that a couple of years earlier, but still representing steady growth.
“We’re still growing,” he said. “A lot is due to our location in the outer growth ring of the metropolitan area. Prices are more affordable here. People feel safer. There’s more open space, with quarter-acre lots. People appreciate that we’ve got a lot of great parks, the Fox River, fantastic businesses and restaurants, great schools. And people are friendly — you can talk to anyone you want.”
The state population reached 12,719,141 in 2025, almost flat from the year before, and down 102,600, or 0.8% from the count in 2020.
Cook County was down 1.6% from 2020 due to population losses during the COVID-19 pandemic.
Nationwide, population growth slowed in a majority of the nation’s 3,143 counties. Among the 2,066 counties that grew between 2023 and 2024, nearly 8 in 10 saw their growth slow or reverse direction in 2025. In many cases, counties already in decline saw losses accelerate.
Meanwhile, 310 of the 387 U.S. metropolitan statistical areas (metro areas) had slower growth between 2024 and 2025 than during the prior year.
These shifts were largely due to lower levels of net international migration, which declined nationwide. Nine out of 10 U.S. counties experienced lower immigration levels.
Some of the country’s most populous counties experienced the greatest impacts from lower international immigration. These counties typically had more births than deaths, which naturally increases population, but they also experienced negative net domestic migration — more people moving out than moving in from other areas of the country. Coupled with reduced international immigration, the result was slower growth or, in some cases, population decline.
“The nation’s largest counties like those in the New York metro area 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 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.”
