*An earlier version of this story misidentified the county with the smallest population. Worth County, the state's smallest county, lost 2.6 percent of its population and now has barely 2,000 residents.
ST. LOUIS — Missouri's population is growing, but very slowly, according to new estimates released Thursday by the U.S. Census Bureau.
The census data show that Missouri's population grew by about 13,000 to 6,021,988 in the one-year period ending July 1. St. Charles County led all Missouri counties with a gain of 3,685 residents. Greene County was next with a gain of 3,255, followed by Boone County (increase of 2,614) and two Kansas City-area counties — Clay (up 2,456) and Jackson (up 2,077).
St. Louis County's population rose 1,117 to put it back over the 1 million mark. But it didn't keep up with its neighbor to the west.
St. Charles County has been growing at a fast rate since the end of World War II and now has nearly 370,000 residents, according to the census. In 1950, it had fewer than 30,000 residents.
Economic opportunity is important, St. Charles County Executive Steve Ehlmann said, noting the growth of business and industry in and near St. Charles County. "I think they're moving to where the jobs are," he said.
Ehlmann said good schools and safe neighborhoods are also important factors.
Jasper County, still recovering from the devastating Joplin tornado of two years ago, had the biggest loss. The census said the county's population dropped by 2,576 residents.
Troy Bolander, planning and community development director for the city of Joplin, believes the town's population is actually starting to turn around. Joplin had just over 50,000 residents before the May 22, 2011, tornado that wiped out about one-third of the homes in the community. City officials believe the population over the next year or so dropped by around 5 percent. Now, Bolander believes people are coming back.
"What we're seeing on the ground is very encouraging," he said, noting that building permits and utility hook-ups are rising. "Even the school district has indicated to us that they're almost at their pre-tornado level."
Some of Missouri's smallest counties got even smaller. Holt County in northwest Missouri lost 3.3 percent of its population, dropping to just 4,655 residents, according to the census. Dade County in southwest Missouri had a drop of 2.8 percent. Worth County*, the state's smallest county, lost 2.6 percent of its population and now has barely 2,000 residents.
Holt County Commissioner Bill Gordon said there simply aren't enough jobs to retain young people.
"A lot of these kids get out of school and go to the cities where they can find jobs," Gordon said. "Farming has changed — there are fewer and fewer family farms like there used to be."
The new data showed that St. Louis' population, which has dropped steadily since the mid-1900s, fell by another 391 to 318,563.
The census numbers are subject to revision.