Buffalo Grove is a village in Lake and Cook Counties in the U.S. state of Illinois. A suburb of Chicago, it lies about 30 miles northwest of Downtown Chicago and 20 miles north of O'Hare International Airport. As of the 2020 Census, Buffalo Grove has a population of 43,212. It totals 9.6 square miles of land, with the top three-quarters in Lake County and the bottom quarter in Cook County. Roads in the village such as Lake Cook Road and Illinois Route 83 converge on I-294.