Napa is the largest city and county seat of Napa County and a principal city of Wine Country in Northern California, United States. Located in …Napa is the largest city and county seat of Napa County and a principal city of Wine Country in Northern California, United States. Located in the North Bay region of the Bay Area, the city had a population of 77,480 as of the end of 2021. Napa is a major tourist destination in California, known for its wineries, restaurants, and arts culture.