International immigration helped drive much of Maricopa County’s growth last year.

The U.S. Census Bureau says that without a net increase in immigration, lower birth rates and the departure of domestic residents would have led the largest counties to see the number of flatlands or declines, according to the latest estimates.

Maricopa County was the third fastest growth, with first place after Harris County in Texas and Miami-Dade in Florida, second place.

Two-thirds of the country’s counties grew last year, with over 100,000 counties growing faster than small counties.

It overturned the trend seen in the first few years of the Covid-19 pandemic.

Immigrants drove in 2024 Overall US population growth The country surpassed 340 million residents, making it the fastest rate in 23 years. The Census Bureau changed the way immigrants were counted last year by including more people hospitalized in the US for humane and often temporary reasons.

“The main driver of the US population growth has long been a birth that exceeds deaths, and this surplus has declined over the past four years, providing a large portion of the country’s population growth.”