Madison County's population, including most of the cities of Huntsville and Madison, grew by 4,700 people last year to reach 361,046, according to U.S. Census figures released today.

"This is what we've been working toward for the past 10 years," Huntsville Mayor Tommy Battle said in a Wednesday statement. "We've planned for this growth as we worked to attract 20,000 new jobs and, in parallel, worked to ensure our roads, infrastructure, education system and quality of life could meet the needs of our community. So, building growth ourselves is what Huntsville does best."

The new estimates show that, while most counties in Alabama are shrinking, Madison County grew 1.3 percent from 2016 to 2017, the fourth fastest growing county in Alabama.

Meanwhile, next-door neighbor Limestone County was the third fastest growing county in the state, adding 1,500 people from 2016 to 2017 to reach 94,402 residents.

The two counties combine to make up the official Huntsville metropolitan area of nearly 455,458 people. Huntsville metro passed Mobile in 2010 to become the second-largest metro in Alabama. Huntsville metro continues to be the only one of the four large metros in Alabama growing rapidly, as Huntsville metro grew 9 percent since 2010.

Population estimates for specific cities won't be released by the Census department until later this spring.

"We continue to build off the assets that are in place," Madison Mayor Paul Finley said of the latest county estimates. "Especially with Redstone (Arsenal) and the growth we're seeing in the different defense industries."

Managing that growth is the challenge now. The FBI is expanding its operations on Redstone Arsenal, and 4,000 new workers will be working and living in the area by 2021 when a new Toyota-Mazda plant opens in Limestone County.

Those new workers will add to the congestion already on Huntsville area roads during morning and evening rush hour and Saturday. Battle said his administration has been working on that, too.

"This growth is the reason we put together the $250 million Restore Our Roads plan for our major corridors, and the reason why we are further investing another $147 million in our internal road network to improve connectivity," Battle said. "We've invested $250 million in new schools, capital funds into new parks, museums, greenways - everything you see is part of our capital plan is to accommodate growth we knew was coming."

Finley's city of Madison, with 48,000 people as of 2016 estimates released last year, now expects more people as the area welcomes the auto plant and its suppliers. A key to the growth is Madison's high-rated schools, he said.

Finley said the city has formed a Madison Schools Growth Impact Committee to advise city and school leaders on future options as more people move to the city. The committee will report to the City Council and school board tonight at 7 in the school system's central office boardroom at 211 Celtic Drive.

Nationally, the growth spurt has made the Huntsville metro area America's 118st largest, just ahead of Corpus Christi, Texas, and just behind Asheville, N.C. In Alabama, the Birmingham metro area comes in at No. 50 on the national list with a population of about 1,489,807 and Mobile metro is No. 130 with a population of 413,955.

Madison County is Alabama's third largest county, behind Jefferson and Mobile. Limestone is now the 14th most populous county in Alabama, having grown past Lauderdale and St. Clair since 2010.

Only two spots are expanding more rapidly.

The new Census figures show Baldwin County remains the fastest-growing county in Alabama with a population of about 212,628. It grew by 5,000 people between 2016 and 2017. Lee County, home to Auburn, continues growing at the second fastest rate in Alabama.

Updated on March 22 at 8:40 am.