California's northernmost wine region also has the westernmost winery in the continental United States: Pacific Star Winery on a bluff overlooking the Pacific Ocean. Running 30 miles inland, Mendocino County calls itself "America's Greenest Wine Region." It encompasses almost 75 wineries, 18 percent of which are certified organic and six percent certified or pending certification as biodynamic. Twenty of the wineries are also certified fish-friendly. (The county is a watershed for the Russian and Navarro rivers.) Parducci, the oldest winery in the region, is 100 percent solar-powered and the nation's first carbon-neutral winery. Chardonnay and cabernet sauvignon dominate the field of varietals in Mendocino wine country, with zinfandel, pinot noir and merlot coming in at the third through fifth spots, respectively.

For more information: Mendocino County

As he documented in Travels With Charley, John Steinbeck enjoyed beer, but the literary legend died just as grape vines were taking hold in his beloved Monterey County. Too bad. Today there are more than 85 vintners and growers, though 70 percent of the grapes are shipped to wineries in other wine regions. You probably wouldn't guess it, but Monterey County grows more chardonnay grapes than anywhere else in the United States. It was, in fact, Chalone Vineyard's 1974 chardonnay that came in third in the famous Paris tasting of 1976 in which California beat France at its own game. Chardonnay, merlot, pinot noir and cabernet sauvignon are the heavy hitters here.

For more information: Monterey County

The big names—Mondavi, Krug, Schramsberg—are here, but so are about 325 more wineries. You'll find their names on Wine Spectator's Top 100 lists and on menus at just about any restaurant without a drive-through window. Touring, though, is the best way to experience Napa's rolling hills and architecturally stunning tasting rooms. In more rural wine regions, you won't find the likes of Castello di Amorosa's authentic Tuscan castle, the Friedensreich Hundertwasser-designed Quixote Winery, or the Frank Gehry-designed tasting room under construction for Hall Wines. Certainly the indigenous Wappo Indians foresaw the future when they called the area Napa ("land of plenty").

For more information: Napa Valley

The United States' oldest commercial winery lies not in California, but in New York's Hudson River Valley. Benmarl Winery produces lesser known varietals such as Baco Noir, Frontenac and Traminette. You likely won't find the label of those or other New York wineries outside of the state. Viticulture is also popular in Long Island (there are a dozen wineries in South Fork!), on the midstate Finger Lakes, near Lake Erie and the in Niagara Escarpment on Lake Ontario (the state's youngest recognized wine region). About a hundred of the states' 240 wineries are in the Finger Lakes area, where the signature wine is Riesling. If you prefer red wines, head for Long Island.

For more information: New York Wines

If pinot noir is your wine, Oregon is your state. The 300-plus wineries know the best results come from working with grapes that like a cool climate. More than 9,800 acres are planted in pinot noir and some 2,600 in pinot gris before the numbers plummet to some 760 acres for the third-most planted grape (chardonnay). Sixteen viticultural areas are concentrated mainly on the west coast, with a few along the state's northern border, and one winery, Wawawai Canyon Winery, is just one mile west of Idaho. On average, Oregon wineries produce 5,000 cases a year; by comparison, Sonoma County's Kendall-Jackson Winery produces four million cases a year. Many of the wines are only available at the wineries, making a visit all the more compelling.

For more information: Oregon Wines

Paso Robles' wine grapes are so good that they end up in a lot of Napa Valley wines, as well as those of other high-profile wine regions. In fact, more than half of the area's wine grapes are exported out of the area. But some 170 wineries have made Paso Robles a wine country of its own. In 1997, Wine Spectator named Justin Vineyards' bordeaux-style blend, Isosceles, one of the top 10 wines in the world. But it's zinfandel that holds the heart of many Paso Robles wineries. In fact, each March, they hold a three-day festival for that one varietal. In the last few years, Rhône grapes have come on strong here. Vintners claim they owe part of their success to a diurnal swing that grapes seem to love; in August, Paso Robles experiences as average 40-degree drop from daytime high to nighttime low, compared to Napa Valley's 29.4-degrees.

For more information: Paso Wines

Known for its beaches and upscale tourist spots, Santa Barbara County is also known among wine-lovers for its pinot noir and chardonnay. But the Southern California wine country has diversified to the point that a tour among its tasting rooms yields unsuspected finds, including dry Rieslings, chenin blancs and Rhône varietals, as well as the usual bordeaux grapes. For those who are pressed for time, an "urban wine trail" allows you to taste the fruits of the vintners' labors among tasting rooms right in town, be that in Santa Barbara, Los Olivos or Los Alamos. But with more than 100 wineries to tempt your taste buds, you should venture into the beautiful countryside if at all possible.

For more information: Santa Barbara County Wines

A little more than an hour's drive north of the Golden Gate Bridge lies a rich heritage of family farming and environmentally conscious practices that distinguish Sonoma County's wine industry. More than 30 percent of the county's vineyard acres are enrolled in a Code of Sustainable Winegrowing Programs. You'll find genuine friendliness; but even more than that, you'll find a sense of humor among Sonoma County's 250 wineries. Case in point: Celebrating 150 years of the family business in 2008, Gundlach Bundschu produced a postcard showing a highway patrol officer having stopped a car and these words: "Sonoma Valley Sobriety Test #2: If you can't say 'Gundlach Bundschu Sesquicentennial,' you shouldn't be driving." If Fido is traveling with you, be sure to sign up for Kunde Estate Winery & Vineyard's dog hike/eco-tours.

For more information: Sonoma County

Given his passion for wine, could Thomas Jefferson have possibly had anything else in mind when he incorporated "the pursuit of happiness" into the Declaration of Independence? To find out, travel Virginia's Monticello Wine Trail and visit Jefferson Vineyards, where Jefferson and Italian winemaker Filippo Mazzei planted wine grapes in 1774—two years before, should your history lessons fail you, the signing of the Declaration. Statewide, you'll find more than 130 wineries. Cabernet franc and viognier are two varietals that Virginia "hangs its hat on," according to the state's tourism department.

For more information: Virginia State

Those who like their wine with water should visit Washington's Puget Sound wine country. In fact, you can find wineries off the mainland on Whidbey, Vachon and San Juan islands. Landlubbers might prefer visiting the Columbia Valley viticultural area or wine country along the southern border with Oregon. More than 550 wineries statewide (expected to grow to 600 by the end of 2008) produce slightly more red than white wines. There are more hours of sun during growing season here than in Northern California. The predominant wines are cabernet sauvignon, merlot and increasingly, syrah on the red side; and chardonnay, Riesling and sauvignon blanc on the white side.

For more information: Washington Wine