The Napa Valley includes 16 AVAs or American Viticultural Areas. Young Inglewood Vineyard makes wine in the Southwestern reaches of the Saint Helena AVA, in the benchland nestled up against the Mayacamas mountains, where soils are gravelly, with lower fertility and excellent drainage.
An AVA, aka appellation, is a region that possesses distinct microclimates and terrains which imprint recognizable characteristics on the wines grown in them. They are given names that reflect their location.
Data supporting a proposed American Viticultural Area is submitted to the government, which decides whether the proposed AVA designation will be granted. The Napa Valley itself was given an AVA designation in 1981.