Arlington Heights is a village in Cook County, Illinois, United States. A northwestern suburb of Chicago, it lies about 25 miles northwest of the city's downtown. As of the 2020 census, the village's population was 77,676, making it the 15th-most populous municipality in Illinois. Arlington Heights is known for the former Arlington Park Race Track, home of the Arlington Million, a Breeders' Cup qualifying event; it also hosted the Breeders' Cup World Thoroughbred Championships in 2002.