In 1976 the wine world popped its cork in surprise when several little-known Napa Valley wines took top honours over a crowd of French competitors in a blind tasting in Paris. In the years since, California has become the fourth leading wine producer in the world, producing 90 percent of all US wine from its 2,000 plus wineries. From Napa and Sonoma to the Gold Country and the Inland Empire, more than half a million acres of the state are planted to wine grapes, which fuel a $35 billion industry.

Much of the success of the state’s wine industry hinges on its casual open-door policy for visitors; each region is home to tasting rooms and wine bars that offer wonderfully easy access. And, depending on when you arrive, you may also stumble on a special event, concert or festival.

Napa is California’s most famous wine region, home to around 400 wineries. Located to the north-east of San Francisco, it produces world-renowned Merlot, Cabernet Sauvignon and Chardonnay. The Napa Valley wine country has dozens of well-known vintners in Rutherford, Yountville, Calistoga and St Helena, which lie on Highway 29. Sip to your heart’s content there or at any of the wineries along a parallel route called the Silverado Trail, home to Stag’s Leap, Sterling Vineyards and Clos du Val. Another way to explore the region is on the Napa Valley Wine Train with carriage options including a restored 1915 Pulllman carriage, an al fresco carriage or a glass topped Champagne vista dome each serving a gourmet three-course lunch or dinner as it meanders through the valley.

Another beautiful wine area in northern California is the Sonoma wine region. While not as famous a name as its neighbour Napa, this area of California produces excellent wines and offers wine trails that are, generally, less crowded. Its unique micro-climates make it a haven for some of the best Pinot Noir and Chardonnay in the state.

Gaining popularity are a handful of viticultural areas close to Napa and Sonoma, such as Mendocino, which generates big, luscious reds such as Cabernet and Zinfandel, and Humboldt County, which, with more than 30 wineries, offers plenty of opportunities for wine tasting.

Coastal areas south of San Francisco are less well-known, but just as visitor friendly. The wines are excellent, the wineries uncrowded, and there’s every chance you might meet the winemaker when you call in. Santa Cruz is home to bottlings of Rhone-style wines such as Syrah, and Monterey’s cool climate generates good Riesling.

Not to be forgotten, the sun drenched Gold Country and Central Valley areas are vineyard-laden, such as Lodi, whose 60-plus wineries produce award-winning Zinfandel and Merlot, while El Dorado Hills and Amador County also produce top Zinfandel. On California’s Central Coast, San Luis Obispo and Paso Robles have become popular tasting venues and home to the highly regarded Chardonnay and Zinfandel. But most famous is there southern neighbour, Santa Barbara County, whose stock value rose as the setting for Academy Award winning film Sideways. Its Mediterranean-style climate generates some of the state’s best Pinot Noir, Syrah and Chardonnay.

Between Los Angeles and San Diego is the still young region of Temecula, where dozens of small producers have created a drive-friendly trail of tasting rooms.

Finally, sustainable wine growing practices are becoming more widespread. Frey Vineyards, in the Redwood Valley, is leading a trend to go beyond organic by becoming certified biodynamic, making the family-owned winery a self-sustaining agricultural entity in harmony with the local ecosystem. Meanwhile, Sustainable Vine Tours in Santa Barbara helps to show visitors the difference between organic wine and wine made from organic grapes so you can sip with a clear conscience.