The name "Napa Valley" has been granted a certification mark by the US Patent and Trade Mark Office, the Napa Valley Vintners trade association announced yesterday.
The designation is a guarantee to consumers that wines bearing the name are actually made from grapes grown in the Napa Valley American Viticultural Area.
Napa Valley wine growers have been frustrated at the extent to which the term Napa Valley has been used by other winemakers, in particular in China.
It is the first time the US Patent and Trade Mark Office has recognised a designation from an American Viticultural Area.
Napa Valley Vintners has spent five years working towards certification, which involved getting the agreement of the 100-plus businesses that already used Napa in their own trademarks.
The trade group has been negotiating protection against passing off from organisations in a range of countries, including Australia, Brazil, India, Thailand and the EU.
J. Scott Gerien, attorney for Napa Valley Vintners, said: "Working with other countries to obtain protection for the Napa Valley name, it became clear we needed similar status here at home to be taken seriously when requesting support outside the US."