Four years after Loudoun’s tourism association launched a campaign to brand the county as “D.C.’s Wine Country,” the marketing slogan has evolved into an undeniable reality: The Loudoun wine industry is on the rise.

Loudoun wine producers were included in this year’s budget presentation to the Board of Supervisors, when County Administrator Tim Hemstreet noted that there are 34 wineries, more than any other county in the state. Tourism officials say the number is expected to rise to 40 by the end of the year.

Late last month, the Loudoun Department of Economic Development announced the sale of Lost Creek Vineyards and Winery — listed among the “Best of Northern Virginia” for 2012 by Northern Virginia Magazine — for $2.3 million.

Loudoun’s tourism association is planning an “epic” wine and culinary event that aims to bring 10,000 visitors to Loudoun over Labor Day weekend.

“In less than 25 years, Loudoun County’s wineries have emerged as the leading Virginia producers of [grape vines] and New World grape wines,” Kellie Boles, agricultural development officer for Loudoun County, said in a statement.

Sebastien Marquet, a winemaker from France who came to Loudoun from Northern California in 2007, said the area is increasingly attracting winemakers who have worked in a variety of environments and who are drawn to a challenge.

“This is not an easy place to make wine,” Marquet said. “The weather conditions are difficult, and it’s difficult to be consistent. So you really need experienced winemakers.” Experienced winemakers are coming, he said, from places such as France, Italy and Spain.

“It is a very attractive region, definitely, for people all around the world,” he said.

Area wine lovers are also coming to Loudoun in mounting numbers, and contributing to the county’s local economy: Beverage manufacturing, which includes wineries, accounts for nearly $5 million in taxable sales each year, Boles said.

Visit Loudoun, the county’s tourism association, recently received positive results on its first wine visitor profile survey, spokeswoman Jackie Saunders said. On average, winery day-trip visitors spend about $350 per visit, and overnight visitors spend nearly $800 per trip, she said.

And they’re happy with their experience, she said. Winery visitors tended to rate their satisfaction at an average of 4.8 out of five possible points, and said they were highly likely to come back, Saunders said. The survey will be done yearly.

Visit Loudoun is in the process of planning its high-end wine and culinary event, “Epicurience Virginia: An Epic Wine and Culinary Experience” for Labor Day weekend, said Visit Loudoun President Patrick Kaler, who gave a presentation on the event to county supervisors this month.

“We’re very excited about the possibilities of this,” he said. “It’s going to have a very, very upscale cachet . . . it’s going to be a big, big event for Loudoun County that we’re very excited about.”

Visit Loudoun expects about 10,000 people at the event, which will be based at Morven Park in Leesburg, Kaler said.

“Epicurience Virginia” aims to further establish Loudoun as a premier wine region, Kaler said.

That goal is supported by winemakers such as Marquet, who is general manager, winemaker and vineyard manager of Doukénie Winery outside Purcellville and who is also an adviser to vineyards in Virginia and California through a consulting business, Burgundy Style Consulting. He will work with the new owners of Lost Creek Vineyards and Winery, Aimee and Todd Henkle, to expand and improve the vineyard’s production, he said.

“The good thing is that they really want to focus on quality and recreate the reputation of Lost Creek, and I’m excited to be part of this,” Marquet said.

“They were producing a lot of sweet wine before, and they really want to change that and make high-quality, dry reds to attract real wine aficionados,” he said.

The Tuscan-style winery, outside Leesburg, includes 21 acres of grapes and a winery with the capacity to produce 7,000 cases of wine per year, according to Loudoun’s Department of Economic Development. Like other popular Loudoun wineries, the property is also designed to host events. Lost Creek has two outdoor pavilions that can accommodate up to 100 guests, a tasting room, a banquet room, a gazebo and a large Colonial home.

The winery will produce a wide range of wines in the coming harvests, including cabernet franc, syrah and petit verdot, as well as traditional Burgundy and Bordeaux wines, Marquet said.

“They have a lot of work to do, but already the 2012 vintage that we produced this year is extremely good, so it’s very promising,” he said.

The wine industry isn’t new to Virginia, Marquet said. Vineyards have grown grapes here for decades. But, Marquet said, he was compelled to come to Loudoun because he observed an increased focus on creating high-quality wines, a trend that he said is gaining momentum.

After six harvests here, Marquet said, “it’s very exciting to be producing world-class wine in Virginia.”