It's been nearly 40 years since Steven Spurrier, a British wine merchant working in Paris, held a blind tasting between the top wines of California and their French counterparts. The "Judgment of Paris," as it became known, surprised many, as a clutch of Californian wines scored higher than examples from Bordeaux and Burgundy. Overnight the world woke up to what Californian winemakers had known all along: Their wines could stand alongside the very best.

In many ways the late 1970s were a turning point for California...