Moline is a city in Rock Island County, Illinois, United States. The population was 42,985 as of the 2020 census, and was estimated at 42,362 in 2025. It is the largest city in Rock Island County and the 36th-most populous in Illinois outside the Chicago metropolitan area. Moline is one of the Quad Cities at the confluence of the Rock and Mississippi rivers, along with neighboring East Moline and Rock Island in Illinois and the cities of Davenport and Bettendorf in Iowa. The Quad Cities metropolitan area had a population of approximately 380,452 as of 2025.