Maricopa County is Fastest-Growing in Nation, According to U.S. Census Data Article originally posted on AZ Central on March 22, 2018 More people moved to Maricopa County than any other county in the country last year, according to U.S. Census Bureau population estimates released Thursday. Maricopa County’s population jumped by nearly 74,000 people — a 1.7 percent increase. The county’s growth helped it maintain its rank as the fourth most populous county in the country, with 4,307,033 residents. Clark County in Nevada saw the next largest gain with a 47,355-person increase. All of the top-10 largest-gaining counties were in the South or the West. The new data only includes population estimates as of July 1, 2017, for counties and metropolitan areas, not individual cities. Although Phoenix overtook Philadelphia as the fifth largest city last year, the Phoenix-Mesa-Scottsdale metropolitan area is only the 11th largest metro area, with 4,737,270 people (the metro area includes part of Pinal County, which is why the metro area population is larger than the county’s). That being said, the Phoenix-Mesa-Scottsdale area added nearly 89,000 people last year, the fourth-largest gain of any metro area. “Post-recession we have worked very hard to build a more sustainable economy — one rooted in education and focused on exports, and it’s working,” Phoenix Mayor Greg Stanton said. He said, “We don’t want to celebrate growth for growth sake,” but in Phoenix and the region there has been a focus on quality employment that will sustain long-term growth. Stanton also noted that people are moving to the county’s center city at a disproportional rate because Phoenix has made investments in transportation and infrastructure that boost quality of life. “We want Phoenix to do great and we want the county to do great,” he said.