Arlington Heights is a municipality in Cook and Lake Counties in the U.S. state of Illinois. A suburb of Chicago, it lies about 25 miles (40 km) northwest of the city's downtown. The population was 75,101 at the 2010 census. It is the most populous community in the United States that is incorporated as a "village", and is the 13th most populous municipality in Illinois, although it is not far ahead of its nearby Illinois neighboring villages of Schaumburg and adjacent Palatine.
Arlington Heights is known for 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. The village is also home to the Arlington Heights Memorial Library, which has one of the largest collections of books in the state.