Percentage of California wine grapes grown in the Napa Valley. Although the name Napa Valley is known around the world, the region itself is rather small. Napa Valley has just 44,000 acres of vines, making it 1/6 the size of Bordeaux. In fact, the Valley represents just 0.4% of the world’s wine production. There are 700 grape growers and 475 physical wineries in the Napa Valley, 92% of which are family owned.