WINDER - Fort Yargo State Park in Winder, with its 18 miles of volunteer-built mountain bike trails, has become a hotspot for urban adventurers who have turned one of the least-used parks in the state into a pedal-fueled economic engine.

The trails, which were completed about five years ago, have attracted race promoters and helped draw previously unseen crowds to the park.

"We used to have some people come in to do hiking and different things," said Park Ranger Eric Bentley, who took over at the park in 2004. "But the mountain bike community has brought a whole slew of people in here who would have never come if we didn't have these mountain bike trails.

"And it's not only that they are coming here, they're bringing in money to eat at restaurants and everything else. People are using this as a destination."

The park attracted close to 400,000 visitors in 2010. Those visitors made a more than $24 million impact on the local economy, according to numbers provided the Friends of Georgia State Parks and Historic Sites.

Each of the springtime races at the park can attract more than 500 participants and their friends and family. The most recent race, a duathlon hosted by Dirty Spokes bike club, attracted about 200 participants and an equal number of supporters.

The vast majority of race participants drive from metro Atlanta, buy gas and supplies in Winder, and eat at least one meal while they are in Barrow County.

When they return to Atlanta, they tell friends about Fort Yargo, and the crowds seem to get bigger every spring, said Tim Schroer, who organizes the Dirty Spokes races. Still, the trails aren't as crowded as other popular tracks in the area, race participants said.

Mountain bikers and runners like the park because the trail loop is longer than most in metro Atlanta, and it's beautiful, with the trail winding around the park's 260-acre lake.

They routinely are compared to trails like Chicopee Woods in Gainesville and Blankets Creek in Woodstock, which are popular with mountain bikers but are fairly well-worn. Yargo is something new.

"This is only 45 minutes from our house," said Tom Schulz of Roswell. "When people first start riding, they usually go to their home trails, then to Chicopee in Gainesville or Big Trees in Sandy Springs, then they think about the North Georgia mountains. People just don't think about coming out to Fort Yargo, but it's so close and it's a good trail."