NAPA, Calif. -- Quick, what's America's biggest wine region? If you answered California's Napa Valley, you're way off thanks to a federal ruling that creates a new one starting today.

It's the Upper Mississippi River Valley, covering 29,914 square miles and encompassing portions of Minnesota, Wisconsin, Illinois and Iowa. That's 39 times the Napa Valley's 759 or so square miles.

The new region is huge news for Midwestern vintners.

"I'm really excited about it," said Paul Tabor, of Tabor Home Vineyards Winery about 40 miles south of Dubuque. "Wine enthusiasts really do look at the labels for an appellation, and now we can use that as part of our marketing story."

American Viticulture Areas, or AVAs, recognize a grape-growing region that may be historically known and that contains specific geological features. The new region was created after area wine and agriculture officials petitioned the Alcohol Tobacco Tax and Trade Bureau, which controls the designations.

Use of an AVA isn't a stamp of approval, but many consumers like the idea of buying wine from a specific area, following the French concept of "terroir" -- that wine should reflect the character of the land it came from.

Though the image of the Midwest might be wide, flat plains, the new AVA falls in an area that was largely skipped by Ice Age glaciers, so instead of being flat it has the steep slopes and well-drained soil required to grow premium grapes.

But there's no getting away from those really cold winters, meaning the familiar grapes of Europe -- chardonnay, cabernet sauvignon -- can't survive here. Wineries must either import juice or grow winter hardy grapes, many of them hybrids developed in France.

Ninety years ago, Iowa was sixth in grape production in the U.S., but that was with the Concord grape, associated with sweeter wines, not today's drier wines.

The wine industry re-emerged in the last decade, surprising some with medals in national competitions, Tabor said.

"Six or seven years ago I got phone calls and e-mails from California wineries -- 'What are these wines of yours winning competitions? We didn't know you could grow grapes in Iowa."'

Though the region is big, the wine industry there is small but growing. Tabor estimates there are about 50 wineries and maybe just 400 acres of vineyards. The Napa Valley's way ahead there. Though only about 9 percent of the area is planted in vines, that still amounts to 45,000 acres.

The new AVA knocks off former No. 1, the 26,000-square-mile Ohio River Valley AVA.

Tabor and others say they had no intention of trying to be the biggest; that was just the region's natural contours.

Once the industry matures, they would like to see the same kind of thing that has happened in California, where smaller regions have petitioned to be recognized as distinctive. Napa Valley, for instance, includes 14 sub-appellations.

Warren Johnson, one of the people who led the quest for a new AVA, isn't expecting the Upper Mississippi River Valley to become Napa's rival any time soon. But he's happy nonetheless.

"It's a recognition of, 'Hey, we can go out and produce some good wines,'" he said. "The AVA designation should help put this region on the map."