The Quad Cities are a group of cities which flank the Mississippi River in Iowa and Illinois in the midwestern United States. The five largest cities, in order of descending population, are: Before World War II, the area was known as the "Tri-Cities", and included only Davenport, Rock Island, and Moline. With the growth of Rock Island County, East Moline was eventually given "equal status" and the region became known as the "Quad Cities" during the early 1960s. By the 1970s, Bettendorf had grown such that many people in the community openly discussed the adoption of the name "Quint Cities". However, by this time, Quad Cities had become known well beyond the area, and Quint Cites never caught on. As Bettendorf passed East Moline in size and prosperity, East Moline was quietly dropped from strictly maintained lists, though East Moliners still regard their town as one of the "Quads".

As a patchwork of similarly located but politically different urban units situated at the edge of the Rust Belt, the Quad Cities area serves as an interesting case study on the effects of various economic, social, political, and environmental variables on the trajectory of municipalities seeking economic recovery. Seen as a single urban mass, the Quad Cities perfectly exemplifies the multiple nuclei model of urban arrangement.