The U.S. wine industry is expanding, and it’s time to get on board.

That was the message photographer Charles O’Rear and his author wife Daphne Larkin delivered to Capitol Hill last week. While touting their recently released book “Wine Across America: A Photographic Road Trip,” the duo mingled with lawmakers, tasting some of the more than 20 wines that were available at a reception Wednesday sponsored by the Congressional Wine Caucus.

The event was the brainchild of Rep. Mike Thompson (D-Calif.), co-chairman of the caucus.

“Wine is now produced in all 50 states. Whether their constituents grow it, make it or consume it, every Member of Congress has an interest in wine issues,” said Thompson, who owns a vineyard in Northern California. “Tonight’s event was a chance for Members to celebrate the passion and spirit of American winemaking. There are hardworking folks in every state who contribute to the American tradition of making great wines, and they should know that Congress appreciates their efforts.”

Larkin and O’Rear are no strangers to wine. This is the eighth book on the subject for O’Rear, a former National Geographic photographer. The couple’s latest endeavor started more than two years ago as they were drinking wine in their Napa Valley home, considering how the number of wineries outside of California had grown. The pair decided to find and photograph vineyards from all 50 states, traveling more than 80,000 miles. While they admit that they physically went to only 40 of the 50 states (skipping out on destinations like North Dakota, which was the last state to enter commercial wine production), the result is a chronicle of vineyards in each state.

“Wine Across America,” which boasts more than 300 photographs, also contains short regional introductions and captions that evoke the essence of winemaking. The authors uncovered some unexpected treasures in their home states. For O’Rear, it was a stone-lined cellar outside of St. Louis that had been aging wine since 1881. Larkin, who grew up in the 1950s going to juice stands in St. Petersburg, Fla., was amazed to find that her childhood favorite had transformed itself into a citrus- producing winery.

“It’s what’s indicative of what’s going on all over the country,” said Larkin, where farmers are taking out traditional crops and planting vines, or using locally produced fruit such as strawberries, pineapple, blueberries and elderberries in wines. Local flavors even crop up in wine produced in Gilroy, Calif., where the specialty is garlic.

O’Rear and Larkin are quick to point out that they did not choose the vineyards based on the typical system that wine experts have devised to rank quality. Instead, they were looking for geographically diverse and interesting scenery, which for the most part came from Internet research and word of mouth. The word-of-mouth finds included a two-man wine-producing operation in Utah. Dwarfed by the rugged red spires of Castle Rock east of Moab, Round Mountain Vineyards and Winery, which produces only 100 cases of chardonnay yearly, is attached to a modest home. The addition of such diamonds in the rough demonstrates O’Rear and Larkin’s efforts to go beyond destination vineyards such as Biltmore, in Asheville, N.C., which gets about 600,000 visitors per year.

“It’s not about quality, it’s about the American spirit,” O’Rear said. The lasting impression for him: “California, just watch out.”