What Cities Constitute The Quad Cities?

There has been an on-going debate for long before I called the Quad Cities home about which cities actually make up the "Quad."

I want you to really give this some thought, so here's some history on how a few river towns along the Mississippi in Iowa and Illinois got lumped together according to the Quad Cities Wikipedia page:

• By the start of World War I, Davenport, Rock Island and Moline began being referred to as the "Tri-Cities." The cities decided to give themselves an identifier because it was a cluster of relatively equal-sized communities beginning to flourish around the same bend of the Mississippi River.
• The next 16 years leading up to the 1930s, East Moline began to catch up in size and was incorporated into the mix with Davenport, Moline and Rock Island. It was from this merger that the term "Quad Cities" came to life.
• Almost 20 years later in 1948 The ALCOA plant in East Davenport opened which skyrocketed the City of Bettendorf's development. At this point, the term "Quint Cities" was birthed, although never really caught on.
• Bettendorf eventually passed East Moline in terms of size which brings us to the popular modern-day definition of the "Quad Cities" constituting Davenport, Bettendorf, Moline & Rock Island.

But, even though Bettendorf may be larger than E. Moline, there are still those that classify the "Quad Cities" as having five surrounding cities, or those that define the QC as the greater Quad Cities Area and toss in towns as much as 50 miles away from the Metro.

Now that you know the background, give us your opinion: To you, what cities actually make up the Quad Cities?