Two Jefferson County cities double in size

The Jefferson County seat of Hillsboro and the tiny tourist town of Kimmswick both doubled in population in the last decade.

In a few other areas of the county, foreclosures may be to blame for a loss of residents, officials say.

Still, the county's population spiked by 10.4 percent over the last 10 years, according to the 2010 census. It had grown 16 percent in the previous decade.

County Executive Ken Waller was not deterred by a slower growth rate. He said that a 26 percent population increase over 20 years — a gain of more than 48,000 residents — is nothing to scoff at.

"That's a huge growth for a county this size," he said.

Waller believes the new residents are transplants from St. Louis and St. Louis County who seek a less urban lifestyle with a tolerable commute. More people could mean more federal money for the county to build and improve roads and bridges, Waller said.

And for a county that depends on sales taxes to fill the county coffers, more residents means more people buying things.

Jefferson County remained the fourth-largest Missouri county in the metro area. It has twice as many people as Franklin County, which came in at No. 5. Jefferson County's growth rate trailed Lincoln, Warren and St. Charles counties, which grew at 35 percent, 33 percent and 27 percent, respectively.