OK. I know it's not much but I did try to tie things together a little more with the title. The suspension bridge above "QUAD CITIES" represents the I-74 bridge spanning the Mississippi River between Moline and Bettendorf as seen in the photo below.
Then I listed the four cities that make up the "Quad" in Quad Cities. Davenport, Bettendorf, Rock Island, and Moline. The text color for each city corresponds to it's color on the game map.
Bonus trivia: While those four cities are considered the Quad Cities today, the original Quad Cities were Davenport, Rock Island, Moline, and East Moline. Since then Bettendorf has grown considerably, surpassing East Moline in size and now is counted instead.