(Bloomberg) - Virginia has become one of the top five viticultural states in the U.S. through its growing number of wine-making operations, generating annual sales of close to $1 billion from around 275 wineries clustered around Monticello and Middleburg, according to state officials visiting London on a trade mission.

Tourism is rising, with 1.6 million visitors to wineries in the state last year, and 2016 marks the 40th anniversary of the Italian winemaker Casa Vinicola Zonin SpA’s investment in Virginia’s Barboursville Vineyard, which it acquired in 1976, the bicentennial of the revolution.

Virginia ranks behind California, Washington, Oregon and New York in terms of its overall number of wineries, according to data on the website of WineAmerica, the National Association of American Wineries. Thomas Jefferson, who drafted the Declaration of Independence and became third president, tried and failed to produce wine in the state in the 1770s from his home in Monticello. Much of the industry has developed in the past four decades.

“We’ve just now won fifth place in the country” for wine production, Virginia Governor Terry McAuliffe said during a wine tasting on a trade mission to London April 28, while Virginia Secretary of Agriculture and Forestry Todd Haymore said that even after record production last year, “we are encouraging more planting,” including through a tax-credit program.

“We run the risk of not having enough vineyard production,” Haymore said, noting that most of the state’s wineries are small family owned operations, even if it does have some high-profile vineyards.