WINE COUNTRY California's first wineries were appendages of the 21 Franciscan missions that were built a day's ride by horseback from each other in a chain reaching from San Diego to Sonoma. The missions produced the wine for sacramental use. Eventually the church gave up making wine, and the art passed into the realm of private enterprise. The most popular route for wine tasting is in the Napa Valley along Highway 29 between Oakville and Calistoga. Not far behind in popularity is scenic Highway 12 in the Sonoma Valley. And edging in fast is an area along Highway 101 north between Petaluma and Ukiah. When visiting these stretches of highway, which are heavily concentrated with wineries, try to remain selective. Experts suggest not planning to taste at more than four wineries in one day. Many wineries have picnic areas. An ideal itinerary is to tour a winery, taste, and then purchase a bottle of wine to drink with a picnic lunch.