Harvey is a city in Cook County, Illinois, United States. The population was 20,324 at the 2020 census. Harvey is bordered by the villages of Dix…Harvey is a city in Cook County, Illinois, United States. The population was 20,324 at the 2020 census. Harvey is bordered by the villages of Dixmoor and Riverdale to the north; Dolton, Phoenix, and South Holland to the east; East Hazel Crest to the south; and Hazel Crest, Markham and Posen to the west.