Château Mouton Rothschild winemaker Lucien Sionneau and Robert Mondavi’s son Timothy made the partnership’s first vintage at the Robert Mondavi Winery in 1979. The following year the partners officially announced their joint venture.
In 1981 a single case of the joint venture wine sold for $24,000 at the first Napa Valley Wine Auction – the highest price ever paid for a California wine. In 1982 Robert Mondavi and Baron Philippe de Rothschild began label design. The partners agreed to choose a name of Latin origin for the joint venture, allowing for easy recognition in both English and French. Baron Philippe announced his choice, “Opus,” a musical expression denoting the first masterwork of a composer. Two days later he proposed an additional word: “Opus One”.