Considered one of the most diverse growing regions in California, the Napa Valley AVA extends roughly 30 miles northward from the San Pablo Bay to the base of Mt. Saint Helena in Calistoga. Just five miles at its widest point, the breadth of the appellation is cradled between the Vaca Mountain Range to the East and the Mayacamas to the West. The first approved American Viticultural Area in California and only the second in the United States, Napa Valley is further defined by the 16 sub-appellations within her boundaries. California's geological history is evident in the unique attributes of these appellations; their diversity of soil, climate, and topography distinguish Napa Valley as a premier winegrowing region.