According to 2015 census estimates, half of the US population lives in these 143 counties (ranked by population): Los Angeles County, California Cook County, Illinois Harris County, Texas Maricopa ...

That’s less than each of the two previous years, during which the region’s population grew by more than 70,000 residents a year. Maricopa County, which was the nation’s highest-gaining ...

The big picture: Maricopa County has been heralded as one of the country's fastest-growing counties for adding nearly half a million people in the past decade — but population estimates show ...

The Census Bureau found that without immigrants, Maricopa County wouldn’t have seen any population growth at all last year.