Moline is a city located in Rock Island County, Illinois, United States. With a population of 42,985 in 2020, it is the largest city in Rock Island County. Moline is one of the Quad Cities, along with neighboring East Moline and Rock Island in Illinois and the cities of Davenport and Bettendorf in Iowa. The Quad Cities have an estimated population of 381,342. The city is the ninth-most populated city in Illinois outside the Chicago Metropolitan Area.