But these wines were sort of California's little secret the rest of the world didn't know about California wines back then. It is certainly true that California did produce a few excellent Cabernet Sauvignons even before World War II - Beaulieu Vineyards Georges de Latour Private Reserve, Inglenook, and Simi come to mind.
The California wine industry really didn't get moving until 40 years ago, and so it is somewhat amazing that the state can boast of a wine that is regarded by many as world class, but Opus One has attained that status. That's no surprise, because European wine regions have been established for hundreds of years. Most of the world's well-renowned wines come from Europe - many of them being either Bordeaux or Burgundy.
Wine Review Online - Opus One: American Royalty