Westchester is a village in Cook County, Illinois, United States. It is a western suburb of Chicago. The population was 16,892 at the 2020 census. The area now known as Westchester was occupied by German farmers beginning in the mid-19th century. Samuel Insull purchased the land in 1924 with plans to develop it for residential use and create an …Westchester is a village in Cook County, Illinois, United States. It is a western suburb of Chicago. The population was 16,892 at the 2020 census. The area now known as Westchester was occupied by German farmers beginning in the mid-19th century. Samuel Insull purchased the land in 1924 with plans to develop it for residential use and create an English-style town. As a result, the town's name and the majority of its street names are of English origin.