Napa County is a county in the North Bay region of Northern California, situated north of San Pablo Bay. It is one of the original counties established at California statehood in 1850, with some of its early territory later transferred to Lake County in 1861. The county seat is the City of Napa, and as of the 2020 census the population was 138,019.
The county is internationally known for its wine industry centered on the Napa Valley, a reputation cemented when local wineries placed first in the 1976 “Judgment of Paris” tasting. Geographically it includes the Mayacamas Mountains and Mount Saint Helena at its northern end.
In the context of the Zodiac case, Napa County is relevant as the jurisdiction containing Lake Berryessa, where the Lake Berryessa attack on Bryan Calvin Hartnell and Cecelia Ann Shepard occurred in 1969. After that attack, the Zodiac Killer telephoned authorities in the City of Napa to report the crime.