America’s most popular winery — at least by one measure — is not in the Napa Valley. Nor is it in Sonoma County or even Monterey. It is in Buncombe County, N.C.

The Biltmore Estate, a resort and winery along the banks of the French Broad River in Asheville, hosts more winery visitors per year — some 600,000 — than any other winery in America.

This surprising wine fact comes from Charles O’Rear and Daphne Larkin, two Napa Valley residents who have put in a lot of miles — 80,000 — to capture the state of the winemaking art in the United States.

Over two years, on planes, in rental cars and beating up their Ford Explorer, Larkin and O’Rear amassed the stunning images and accompanying words for their latest book, “Wine Across America,” scheduled for publication in November.

They may not have discovered a cabernet to match Diamond Mountain’s finest, or a vineyard as celebrated as To Kalon. But then again, O’Rear said, “It is not about vineyards. In other states, people are making wine from all kinds of other things — honey, huckleberries, blueberries.”

During their journey, the two veteran journalists discovered what Larkin said is “the wine story of the century.”

“We believe that there is an American wine revolution going on out there,” she said. “Not only is every state officially making wine, everyone is doing it with great gusto.”

Before moving to Napa, Larkin wrote for Newsweek magazine’s international edition and traveled the world covering the United Nations as an in-house correspondent, preparing information for other journalists. She also wrote a column in Parenting magazine for a decade.

O’Rear has published several books of photography about wine — including “Chardonnay,” “Cabernet” and “Napa Valley: The Land, the Wine, the People.” For years, he worked for National Geographic magazine, shooting everything from the wilds of Indonesia and a Russian village to portraits of bacteria.

In their “Wine Across America” journey, O’Rear and Larkin generally did not see the elaborate chateaux and state-of-the-art facilities that have come to define the Napa Valley. Instead, they saw old-fashioned American can-do spirit applied to the ancient craft of turning fruit, yeast and water into wine.

They visited a winery in an abandoned coal mine in Kentucky, an Alaskan winery hundreds and hundreds of miles from the nearest vineyard, a Colorado winery with what is touted as the highest-altitude vineyard in the world, wineries in basements, old bordellos and converted churches.

Among the people they met, “there’s a similarity” with the winemakers of the Napa Valley, said O’Rear, and a difference, too.

“The people I know around here make wine because its a passion. For some its about making money, for some its about pride. Uniformly, at every winery we went to, people were making wine because they just loved doing it. They loved working with the soil, the earth, and making the wine.”

Larkin identified several factors contributing to the revolution: “Remarkable improvements in regional winemaking, increased media coverage on winemaking, consumer-friendly decisions on interstate shipping, quality wine at lower prices.”

A wine culture, the American strain of the ages-old European tradition, is coming into its own. “In Napa Valley, we’re used to having a glass of wine with dinner,” said Larkin. “But it’s also happening in Arkansas, Florida and Utah.”