[Tadhg]

The first vineyard in california was at the Mission San Diego in 1769, but they never sold the wine...so I guess it wasn't "commercial"

[Clemenza]

You are correct. Let's not forget that Father Serra planted "Mission Grapes" (similar to Carignano grapes from Sardinia) at every mission he founded. Since they were all produced for Mass, they were not sold commercially. The first commercial vineyards were, therefore, in LA County.

[hedgetrimmer]

Don't forget Agoston Haraszthy (1812-1869),
"Father of Modern Viticulture in California" and author of Grape Culture, Wines and Wine-Making, with notes upon Agriculture and Horticulture