The urban core consists of four principal cities: Davenport and Bettendorf in Iowa, and Rock Island and Moline in Illinois.
These cities are the center of the Quad Cities Metropolitan Area, which as of 2013 had a population estimate of 383,781 and a CSA (Combined Statistical Area) population of 474,937, making it the 90th largest CSA in the nation.
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.
At the time of European encounter, it was a home and principal trading place of the Sauk and Fox tribes of Native Americans.
The treaty resulted in the Native Americans ceding six million acres (24,000 km²) of land to the United States in exchange for a much smaller reservation elsewhere.
Black Hawk State Historic Site in Rock Island preserves part of historic Saukenuk and is listed on the National Register of Historic Places.
These rapids were difficult for steamboats to traverse.
For 14 miles (21 km) between Le Claire, Iowa, and Rock Island, the Mississippi River flowed across a series of finger-like rock projections protruding from either bank.Today, the rocks are submerged six feet underwater by a lake formed by two locks and dams.Over time, a minor industry grew up in the area to meet the steamboats' needs.Boat crews needed rest areas to stop before encountering the rapids, places to hire expert pilots such as Phillip Suiter, who was the first licensed pilot on the upper Mississippi River, to guide the boat through the rocky waters, or, when the water was low, places where goods could be removed and transported by wagon on land past the rapids.Saukenuk was the principal village of the Sauk tribe and birthplace of its 19th-century war chief, Black Hawk.
In 1832, Sauk chief Keokuk and General Winfield Scott signed a treaty in Davenport after the US defeated the Sauk and their allies in the Black Hawk War.