KYLE — Husband-and-wife team Spencer Thomas and Julie Albertson had modest goals when they moved their wholesale pie business out of their Austin home and opened the Texas Pie Company in downtown Kyle in 2000.

"I can remember making the comment that if we could get $75 a day (in business) that we could make our mortgage," Thomas said.

In the 10 years since, much has changed, for the Texas Pie Company and for the surrounding area.

Its first few years, the shop sold about 800 pies at Thanksgiving, Thomas said. Last Thanksgiving, "we sold more than 3,000," he said.

Texas Pie now has six employees and a lunch menu.

That success is emblematic of what's going on across Hays County these days. The county's population has risen 67.4 percent in the past decade, to about 164,000, making it the fourth fastest-growing county in Texas and 15th in the nation, according to the U.S. Census Bureau.

Much of that growth has been in the northern part of the county, especially in Kyle, which city officials say is projected to overtake San Marcos as the county's largest city in the next five to seven years.

Kyle's population has risen about 600 percent in the past decade to an estimated 32,000, according to the city.

Kyle also has become the retail hub of northern Hays County. At a time when retail development has slowed in other parts of Central Texas, Kyle has about 2.5 million square feet of new development open or under construction at one busy intersection alone, according to the city. By comparison, the largest single shopping development in Austin, Southpark Meadows, has about 1.6 million square feet.

The city's sales tax revenue has risen about 500 percent in the past decade — ahead of Williamson County cities such as Cedar Park and Leander.

The junction of Interstate 35 and Kyle Parkway (FM 1626) has created a sort of second town center away from the city's still-sleepy downtown.

The growth there occurred after the City of Kyle partnered with the Texas Department of Transportation to build an overpass and create an exit at the site, said Diana Blank, the city's economic development director.

On one side of Kyle Parkway is the 230,000- square-foot Kyle Marketplace, which is anchored by a 150,000- square-foot H-E-B Plus store. Across the road is Kyle Crossing, which includes a Target and a Kohl's department store.

"When you see stuff like ... banks and grocery stories going in, it's a sign that the population is viable" for business, said Rob Adams, a lecturer at the University of Texas' McCombs School of Business. "Think of the population, think of the housing base, the tax base that brings in."

Just across the interstate from all those new stores is the centerpiece of the new Kyle: Seton Medical Center Hays. The hospital is part of a development that is expected to eventually have about 1 million square feet of retail space.

The $144 million hospital, which opened in October, brought in more than 400 direct jobs and has created an estimated 1,500 spinoff jobs in the medical field, Blank said. As a result, "we're kind of naturally flowing to that, toward becoming a medical hub," said Blank, who said an additional 600,000 square feet of medical office space has been built in Kyle because of the hospital's arrival.

Seton was serving about 25 percent of Hays' population through its Austin hospitals, said Thomas Gallagher, president and chief executive officer of the Seton Family of Hospitals' south market. "We studied the demographics and the projections for growth ... and building somewhere within Hays made sense."

Just down FM 1626 from the new retail is Plum Creek, one of the housing developments that have sprung up in Kyle to meet Hays County's population growth. The 2,200-acre community is modeled after urban neighborhoods, with narrow streets, front porches on every house and schools, retail and services nearby.

Plum Creek currently has about 1,500 homes. Plans call for that to swell to 8,700 by the time the project is complete, according to the development's Web site.

One reason for the housing boom, experts say, is pretty obvious: It costs less to live in Hays County than in Travis County.

The median price for existing homes in Hays County in 2009 was $170,000, according to the Austin Board of Realtors. That compares with $205,000 for Travis County.

"There's still lots of land for expansion here, and land prices are much more reasonable in Hays County than in most of Travis or Williamson counties," said William Chittenden, chairman of the Department of Finance and Economics at Texas State University's McCoy College of Business Administration.