The history of urban settlements in the Quad Cities was stimulated by riverboat traffic. For between LeClaire, Iowa, and Rock Island, the Mississippi River flowed across a series of finger-like rock projections protruding from either bank. These rapids were difficult for steamboats to traverse. As demand for river-based transportation increased along the upper Mississippi, the navigability of the river throughout the "Rock Island Rapids" became a greater concern. 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. Today, the rocks are submerged six feet underwater by a lake formed by two locks and dams.