Immigrants kept the largest U.S. urban counties, including Maricopa, growing last year.

But others like Pinal County owe their growth to an influx of domestic residents, according to population estimates from the U.S. Census Bureau released Thursday.

Core counties in the Houston, Miami and Phoenix metropolitan areas grew more than any others in the country primarily because of people moving in from outside the United States, numbers show.

Without the international migration, Maricopa County, Harris County, Texas, and Miami-Dade County would have had nobody moving there last year.

That's because more people already living in the country moved out of than into those counties. Miami-Dade County would have lost population without the immigrants, since the number of births outpacing deaths wasn't enough to overcome the tens of thousands of residents who moved out.

Immigration in 2024 drove the overall U.S. population growth to its fastest rate in 23 years as the nation surpassed 340 million residents. The Census Bureau changed how it counted immigrants last year by including more people who were admitted to the U.S. for humanitarian, and often temporary, reasons.

“A substantial excess of births over deaths has long been the primary driver of U.S. population growth, but as this surplus dwindled in the last four years immigration provided the bulk of the nation’s population increase,” Kenneth Johnson, a senior demographer at the University of New Hampshire, said in an email.

Domestic vs. international migrants

The 2024 estimates reflect a continued dissonance this decade between where current U.S. residents and immigrants choose to live. Immigrants last year moved to the urban cores of metro areas, while those already living in the country preferred counties in the far suburban reaches of metro areas.

The most popular counties for international migrants last year were Miami-Dade and Harris counties, followed by Los Angeles County and Cook County, Ill., which is home to Chicago.

The most popular counties for domestic residents last year were Pinal County, Montgomery County, Texas, north of Houston; and Pasco County, Fla., northeast of Tampa. Also at the top ranks were Polk County, Fla., located between Orlando and Tampa, and Collin County, Texas, in the far northern suburbs of metro Dallas.

New York is on the rebound

When the COVID-19 pandemic hit the U.S. in 2020, the New York metro area and others with some of the densest populations in the U.S. lost tens of thousands of residents to relocation.

But the region has been on the rebound since the pandemic subsided. The New York metro area — the largest in the U.S. with 19.9 million people — added more people than any other metropolitan area in the country last year. As 147,000 residents moved out, nearly 288,000 immigrants moved in, including tens of thousands who arrived on buses provided by the state of Texas. San Francisco and Washington, D.C., are other metro areas that have gained population through international migration, after initially losing them during the pandemic.

The New York metro area also had the nation's largest natural growth last year, with nearly 214,000 births outpacing 141,000 deaths.

South Florida last year jumped two spots over metro Washington and metro Atlanta to become the sixth most populous metropolitan area in the United States. Metropolitan Charlotte, North Carolina, bypassed metro Baltimore for the 21st spot. Among counties, Tarrant County, Texas, home to Fort Worth, leapfrogged over San Bernardino County in South California as the nation’s 15th most populous county.

Deaths outpace births in two-thirds of U.S. counties

Nearly two-thirds of the United States' 3,144 counties grew last year. At the same, deaths outpaced births in two-thirds of U.S. counties, reflecting the reliance on immigration for growth throughout the United States in the years since the start of the pandemic. Nationwide, last year's natural growth was less than half the average gain of 1.2 million people that the country experienced in the five years before the pandemic, Johnson said.

"These recent levels of natural decrease are unprecedented," Johnson said.

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