When John Willie moved to Washington County some 40 years ago, he remembers that St. George was a small town and that the county had a population of 10,000.

Now, Willie, the county's administrator, says, "It's changed a bit."

Anchored by St. George, Utah's "Dixie" is widely becoming known as a retirement mecca, college town and ideal place to raise a family.

It's also ranked first in Utah and No. 34 nationally in growth, according to a new U.S. Census Bureau report based on July 1, 2004, population estimates.

The county's one-year growth rate was estimated at 5.2 percent. It added 5,436 people in one year, growing to an estimated 109,924 people, according to the census report released Thursday.

"I can see why people want to come here," Willie said of Utah's sun belt, which is seeing an increasing influx of young families from Southern California and the Wasatch Front.

Willie says he doesn't know if the growth rate is "totally sustainable in the long term."

"At this point and time, there appears to be no end in sight," he said. "We're selling sunshine. . . . That's quite a commodity."

Utah as a whole had an estimated population nearing 2.4 million. The state had a growth rate of 1.6 percent and added an estimated 36,920 people, according to the census.

Robert Spendlove, manager of demographic and economic analysis for the Governor's Office of Planning and Budget, said the growth is likely even faster-paced than the census estimates. That's because the Utah Population Estimates Committee believes the Census Bureau has underestimated migration into Utah, Spendlove said.

In Washington County, for example, the census showed the county gained about 4,000 people through net in-migration; the state's estimates show about 6,000 people moved into the county, he said. In the case of Salt Lake and Utah counties, the census showed a net out-migration, but the state's estimates showed people moving in, he said.

"The methods we use at the state level are more indicative of the true population growth in Utah," Spendlove said.

Pam Perlich, senior research economist at the University of Utah's Bureau of Economic and Business Research, said international migration remains a significant factor in Utah's growth.

The state's foreign-born population has more than tripled since the 1980s to 158,664 in 2000, Perlich said. Estimates since then suggest the growth continues, she said.

Utah's population growth is largely due to a high birthrate — Utah had a record 50,527 births last year, Spendlove said. The state's fast-growing economy is also attracting new residents, he said.

"Nearly three-fourths of the population growth statewide is due to our children and grandchildren," Spendlove said. "Migration puts us over the top."