Ontario, city (1990 pop. 133,179), San Bernardino co., S Calif., near Los Angeles, in a region of vineyards; inc. 1891. Manufactures include aircraft and aircraft parts, aerospace vehicle parts, sporting and leather goods, wine, electrical equipment, and plastics. High-technology industries in the southern California area have added to Ontario's development; it was one of the fastest-growing U.S. cities in the late 20th cent. Founded in 1882 as a planned community, the city is the site of an international airport and Ontario Motor Speedway.