According to recently released population estimates from the U.S. Census Bureau, immigration played a critical role in the growth of major urban counties in the United States last year. Core counties within the metropolitan areas of Houston, Miami, and Phoenix experienced significant population increases primarily due to people moving in from outside the country.

Without international migration, three of the largest urban counties – Harris County in Texas, Miami-Dade County in Florida, and Maricopa County in Arizona – would have seen no population influx. In fact, Miami-Dade County would have faced a population decline without immigrants, as the region's births failed to surpass deaths and the number of residents moving out was substantial.

In 2024, immigration contributed to a surge in the overall U.S. population, marking its fastest rate of growth in 23 years, surpassing 340 million residents. Notably, the Census Bureau revised its counting methodology to include a broader range of immigrants, particularly those entering the U.S. for humanitarian and often temporary purposes.

Kenneth Johnson, a senior demographer at the University of New Hampshire, noted that while a surplus of births over deaths has traditionally driven U.S. population growth, this trend has changed in recent years. As the natural population increase has dwindled, immigration has become a vital component of population growth across the nation.

The 2024 estimates further illustrate a divide between the living preferences of current U.S. residents and immigrants. Last year, immigrants chose to settle primarily in urban centers, while domestic populations gravitated towards the outer suburbs of metropolitan areas. The counties that attracted the most international migrants included Miami-Dade, Harris, Los Angeles County, and Cook County in Illinois (home to Chicago).

Conversely, the most popular counties for domestic migrants were primarily suburban areas such as Montgomery County in Texas (north of Houston), Pinal County in Arizona (southwest of Phoenix), and several counties in Florida, including Pasco and Polk, as well as Collin County in the northern suburbs of Dallas.

Interestingly, the New York metropolitan area, which faced significant population losses during the COVID-19 pandemic, began to recover once the situation improved. With a population of 19.9 million, it added more people than any other U.S. metropolitan area last year. While 147,000 residents relocated from the area, it welcomed nearly 288,000 immigrants, many of whom arrived via buses organized by the state of Texas. Other major urban areas that gained population through international migration included San Francisco and Washington, D.C.

In addition to immigrant-driven growth, the New York metro area also recorded the nation's largest natural population increase, with nearly 214,000 births outnumbering 141,000 deaths last year. South Florida surpassed the Washington and Atlanta metropolitan areas to become the sixth most populous region in the nation, while Charlotte, North Carolina, moved ahead of Baltimore to occupy the 21st position.

Despite overall population growth in two-thirds of the 3,144 counties across the United States, it’s important to note that deaths exceeded births in a large portion of these regions. This trend underscores the increasing reliance on immigration for population growth, particularly since the onset of the pandemic. Kenneth Johnson highlighted that the current natural decrease levels are unprecedented, with last year's natural growth being less than half of the average gain of 1.2 million people seen in the five years preceding the pandemic.

The data paints a complex picture of population dynamics in the U.S., with immigration emerging as a vital element in many counties’ growth trajectories amidst demographic changes and migration trends.