Louis M. Martini Winery is a Napa Valley producer founded in 1933 in what is now the St Helena AVA. It exclusively produces red wine with a focus on, and reputation for, Cabernet Sauvignon. Louis Martini had been making and selling wine during Prohibition for sacramental and medicinal purposes through his LM Martini Grape Products Company. When the Volstead act was repealed in 1933, the Louis M. Martini Winery was founded and became one of the first five wineries established in Napa post-Prohibition. In 1938, Martini expanded into Sonoma County with the Monte Rosso Vineyard, named for the red volcanic soils of the region.