"It tells me we are bringing business here," said Barry Malonis, marketing coordinator for the Frederick County Economic and Community Development Commission.
The commission has been trying to lure more businesses to the county to offset the 30,000 people who commute to jobs out of the county, he said.
The second fastest-growing county in the area was Berkeley County, W.Va., which saw a 16.6 percent growth in population. With 69,072 residents, it is the seventh most populous county in the state, up from eighth in 1990.
In West Virginia, the Eastern Panhandle's growth was surpassed only by Putnam County, which had a 17.2 percent increase in number of residents.
Berkeley County has grown faster than neighboring Jefferson County, which had a gain of 11.6 percent and Morgan County, with an 11.1 percent increase.
Berkeley County has grown fast because Interstate 81 is a big draw for business and industry, said Ken Green, executive director of the Eastern Panhandle Regional Planning and Development Council.
"Out of economic theory, it's the growth center for the (Eastern Panhandle) region," Green said.
But the I-81-theory doesn't hold true for Washington County and Franklin County, Pa.
Even though the interstate bisects both counties, each county grew by less than 1 percent a year.
One county in the Tri-State experienced a population decline from 1996 to 1997, the government figures show.
The census estimated that Morgan County, W.Va., had 13,477 residents in 1997, which was 47 fewer than lived in the county a year earlier.
But County Manager Bill Clark said he hasn't seen a slowdown in building permits or anything else that would indicate a population loss.
"I seem to see more people I don't know every day," he said. "I think our growth has been steady and manageable growth. That's one of the things I like about our community."
Green said the census numbers are only estimates that tend to be less reliable with smaller populations.
The closing of Vanguard Industries, which idled 86 workers in 1996, might have skewed the government predictions, which are partly based on job losses, he said.