Clarendon Hills is a village in DuPage County, Illinois, United States. The population was 8,702 at the 2020 census. It is a south-west suburb of Chicago. The area that is now Clarendon Hills was a wide, rolling prairie bordering the east side of Westmont. Most of the older villages in Downers Grove Township were built on the same street grid as the Village of …Clarendon Hills is a village in DuPage County, Illinois, United States. The population was 8,702 at the 2020 census. It is a south-west suburb of Chicago. The area that is now Clarendon Hills was a wide, rolling prairie bordering the east side of Westmont. Most of the older villages in Downers Grove Township were built on the same street grid as the Village of Downers Grove. Instead, Clarendon Hills was built to resemble nearby Riverside, a planned, park-like suburb designed by Fredrick Law Olmsted in the late 1800s. Its long winding streets go with the natural contour of the land, rather than extending straight through from the neighboring towns. In 1923, at the time of incorporation, Clarendon Hills had a population of under 900 people. The area was incorporated to avoid annexation by the nearby community of Hinsdale.