Flagler's population swelled by 10.7 percent between July 1, 2004, and July 1, 2005, the report said. Six of the top 25 counties are in Florida.

Flagler County has also been the fastest-growing county in the nation compared to the 2000 Census, with a 53 percent population increase.

"I don't know that this is a real surprise to any of us," said Linda Jarosz, executive director of the Flagler County Chamber of Commerce. "None of us is thinking that it is going to slow down in the next couple of years for our area."

The 76,410 residents living in Flagler on July 1, 2005, was 7,394 more than the population a year earlier, the report said.

Volusia County, which grew by 2.3 percent, did not make the Census Bureau's top 100 fastest-growing counties but posted the 51st largest numerical increase -- 11,104 -- of the nation's counties, according to the study. Volusia's estimated population was 490,055 in 2005.

Jarosz said such rapid growth attracts the attention of major employers seeking a large employee pool and retailers seeking population centers for new stores. And construction and home sales represent large segments of the local economy.

But the new residents also exacerbate existing problems.

The county's school district is scrambling to keep pace with the number of children entering its classrooms, and roads that handle the increased traffic need improvement and expansion, Jarosz said.

Flagler's growth over the past four decades has been fueled by new home construction in Palm Coast, a community platted in the late 1960s and designed to hold 224,000 residents. Last year, the Census crowned Palm Coast as the nation's fastest-growing "micropolitan" city -- growing from less than 50,000 in 2000 to more than 63,000 in 2003.

County Commission Chairman Jim Darby said he hopes the latest report can help loosen state coffers. "Now if we can only get the state Legislature to recognize that growth and get them to give us the funding for the new schools we need -- estimated at one a year for the next 15 years -- we might be in better shape," he said.

On the positive side, Darby said, the growth speaks well for Flagler County and its municipalities as being among the most desirable places in the state and the nation for relocation.

The report also said Maricopa County, Ariz., which includes Phoenix and Scottsdale, recorded the largest population gain since the 2000 Census, adding 563,000 residents.

Flagler County's population increase will likely not be as impressive in next year's Census report. As the national housing market slowed, permits for single-family residential units declined 31 percent in Palm Coast between the 2004 and 2005 calendar years.