during the 1970s a system was established to identify appellations of origins, using the term american viticultural areas (ava). an ava guarantees that a minimum of 85% of the wine in the bottle comes from grapes grown in that ava. the use of individual vineyard names guarantees that 95% of any wine using a vineyard name must be made from grapes grown in that vineyard, and from within a recognized ava. there are 238 avas, of which 138 are in california.