The largest urban counties in the United States continued to grow last year, primarily due to international migration, according to new population estimates from the US Census Bureau.
Core counties in metropolitan areas such as Houston, Miami, and Phoenix experienced significant population gains, offsetting the ongoing trend of domestic residents relocating to suburban and exurban areas.
Without this influx of immigrants, several of these urban counties would have experienced little to no growth. The data highlights the evolving role of immigration in sustaining population increases, particularly as natural growth—births exceeding deaths—declines across much of the country.
Immigrants Sustain Urban Growth as Domestic Migration Shifts
International migration played a decisive role in boosting the populations of key metropolitan areas.
According to the Census Bureau, Harris County, Texas; Miami-Dade County, Florida; and Maricopa County, Arizona recorded some of the largest increases, primarily due to people arriving from outside the United States. In contrast, more domestic residents left than moved into these counties, meaning immigration was the sole driver of their growth.
The Census Bureau’s latest estimates show that Miami-Dade County would have experienced a net population decline without the contribution of immigrants, as the number of births was insufficient to counterbalance the large outflow of domestic residents.
Other major counties benefiting from international migration included Los Angeles County, California, and Cook County, Illinois, home to Chicago.
At the same time, domestic migration patterns reveal a shift away from urban cores. The most popular destinations for people relocating within the US were suburban and exurban counties, such as Montgomery County, Texas; Pinal County, Arizona; and Pasco County, Florida.
This trend suggests a growing preference for lower-density areas outside major metropolitan centres, even as international migrants continue to settle in large urban hubs.
New York Rebounds While Natural Population Growth Declines
The New York metropolitan area, which saw a significant population decline during the COVID-19 pandemic, has since experienced a resurgence.
According to Census data, New York added more residents than any other metro area in 2024, despite continued domestic outmigration. Nearly 288,000 immigrants moved into the region, offsetting the departure of approximately 147,000 domestic residents.
This rebound is mirrored in other major cities that saw population declines during the pandemic. San Francisco and Washington, D.C. have also recorded population growth driven by international migration, suggesting a broader trend of recovery in high-density urban centres.
However, across the United States, natural population growth has slowed significantly. Nearly two-thirds of US counties recorded more deaths than births last year, reflecting an ageing population and declining birth rates.
Kenneth Johnson, a senior demographer at the University of New Hampshire, noted that the nation’s natural growth in 2024 was less than half the average gain recorded in the five years before the pandemic.
