Start-up communities along Utah County's northern boundary continue to lure young families searching for a quiet locale on the outskirts of Utah's major metropolitan area.

But if home construction continues at its current pace, these bedroom communities may soon become bust- ling cities.

New U.S. census estimates released today show the top four fastest-growing cities in Utah during the past five years hug the line between Salt Lake and Utah counties, impressive since a few of these places didn't even exist 10 years ago.

Saratoga Springs, which touches the northwest side of Utah Lake, officially became a town in 1997 with just over 200 residents. Three years later, the population topped 1,000. And just four years after that it raced past 5,000, for a five-year growth rate of 402 percent, making this one-time ranching community the state's fastest-growing city.

"It surprised me five years ago that a town was blossoming out of the sagebrush," said Mark Edwards, Saratoga Springs' public works director.

Farmland still covers most of the land surrounding the city's 14 growing subdivisions, while stores are starting to sprout along narrow two-lane roads. Motorists contend with tractors as they make their way to and from their modern homes.

A year ago the Harrison family moved to Saratoga Springs' Sunrise Meadows, a subdivision in the foothills above the light-blue waters of Utah Lake. From their front porch they can see the snow-capped mountains that surround their brown stucco home.

AnnElise Harrison said her brother-in-law, who lives in American Fork, used to joke with her that their new neighborhood in Saratoga Springs was just this side of the "welcome to Nevada" sign. "People think Saratoga Springs is way out here," she said. "It was something that even made us hesitate about moving out here, but it's really not that far away."

Nothing seems to slow the booming home construction. The economic slump that followed the Sept. 11 terrorist attacks didn't dampen growth. Fluctuating interest rates seem to be an afterthought.

And the growth appears to be speeding up.

During the three month period between April and June, Saratoga Springs approved more building permits for homes than ever before. The city is now averaging between 45 and 55 single-family permits a month, City Manager Ken Leetham said.

Herriman City, on the southern tip of Salt Lake County, can sympathize with the ever-changing landscape of Saratoga Springs. Herriman grew 334 percent from 2000 to 2004, according to census estimates and had a July 1, 2004, population of almost 8,000.

Eagle Mountain, just down the road from Saratoga Springs, has grown 208 percent.

Most of the move-ins appear to be young families with children relocating from elsewhere in Salt Lake and Utah counties, according to Glenn Graham, Herriman city planner.

Officials in these cities attribute their booming growth to an already-crowded valley that has lost much of its small-town atmosphere.

Melanie Christensen and her family moved to Highland - the sixth fastest-growing city - two years ago from American Fork because they liked the ''rural feel.''

They remain close enough to Utah's population center to enjoy the conveniences and far enough away that her boys can "walk around the block and feed the horses."

Safe streets and watchful neighbors also were a welcome benefit for the Harrisons in moving to Saratoga Springs. The family recently rebuilt a retaining wall to include stairs up to their neighbor's yard so their three children could play with the neighbor's kids.

They also enjoy the big box stores available to them in nearby Lehi.

"We don't even have to go to Salt Lake anymore," Dan Harrison said. The Harrisons' commute is now less than 15 miles, thanks to job growth in the area.

mcanham@sltrib.com; mbuckhalter@sltrib.com