Chico (chēˈkō) [key], city (1990 pop. 40,079), Butte co., N Calif., in a region noted for its almond and walnut production; inc. 1872. Olives, kiwi fruit, grain, and nursery stock are also grown, and cattle are raised. Principal manufactures are processed foods, aircraft parts, and beer. California State Univ. Chico is there. Lassen Volcanic National Park is nearby.