In the early days of navigation on the Mississippi, two important rapids were found to interrupt the passage of vessels at low water stages; one, about fifteen miles in length, being above the city of Rock Island, Ill., and the other, about eleven miles in length, above the city of Keokuk, Iowa. These became known, respectively, as the upper and lower rapids. The latter are also called the Des Moines rapids because of the situation above the mouth of the Des Moines River.
Proceedings of the Iowa Academy of Sciences
©1898 Iowa Academy of Science, Inc.
"The Lower Rapids of the Mississippi River,"
Proceedings of the Iowa Academy of Science, 6(1), 74-93.
Available at: https://scholarworks.uni.edu/pias/vol6/iss1/16