1. a city in Napa County in westcentralCalifornia, USA, located about thirtyfive miles (56.3 km) northeast of San Francisco. Napa was incorporated in the late 1800s and became the center of a famous wine- producing and tourist area. 2. a reference to the Napa State Hospital, a state mental institution located in Napa. The institution is a majoremployer for the area.