
1) Amtrak route 2) Metropolitan area of Iowa
Found on
https://www.crosswordclues.com/clue/quad-cities

The name `Quad Cities` for a group of five has resulted from the history of the community. ==History== ===Early history=== Before European settlers came to inhabit the Quad Cities, the confluence of rivers had attracted many varying cultures of indigenous peoples, who used the waterways and riverbanks for their settlements for thousands of years.....
Found on
http://en.wikipedia.org/wiki/Quad_Cities

complex of cities at the Iowa-Illinois border, on the Mississippi River, U.S. Despite its name, the region includes five main cities: Rock Island, ...
Found on
http://www.britannica.com/eb/a-z/q/3

the cities of Davenport and Bettendorf, Iowa, together with Rock Island and Moline, Illinois.
Found on
https://www.infoplease.com/dictionary/quad-cities
No exact match found.