Ontario is a city located in south west San Bernardino County, California, United States, 35 miles east of downtown Los Angeles. Located in the western part of the Inland Empire region, it lies just east of the Los Angeles county line and is part of the Greater Los Angeles Area. As of the 2010 Census, the city had a population of 163,924, down from 170,373 at the 2000 census, making it the county's fourth most populous city after San Bernardino, Fontana, and Rancho Cucamonga.
The city is home to the LA/Ontario International Airport which is the 15th busiest cargo airport in the United States. Ontario handles the mass of freight traffic between the ports of Los Angeles and Long Beach and the rest of the country. It is also the home of Ontario Mills and former home of the Ontario Motor Speedway.