Charles Krug pressed the valley's first commercial vintage in 1861; Prohibition nearly erased it, save for the cellars that survived on sacramental wine. In 1968 the county voted the Agricultural Preserve — the first in America — fencing the vineyard against the suburbs, and in 1976 the Judgment of Paris set Napa Cabernet and Chardonnay above famous French names in a blind tasting that redrew wine's map.
The valley floor's alluvial fans and the volcanic mountain AVAs make two distinct schools of Cabernet. The history keeps a cautionary note: phylloxera returned in the 1980s on a vulnerable rootstock and forced wholesale replanting, and the sharpshooter that spreads Pierce's disease still patrols the state line.