Rock Island at left of map, Davensport Island rightmost labeled island.; Photocopy.; Relief shown by hachures.; "25th Cong., 2nd sess., Senate Doc. no. 139"--upper right within neat line.; "Courtesy of the Army Corps of Engineers, Rock Island Aresenal, 1/80"--lower right outside neat line. 25 x 85 centimeters Scale approximately 1:800; 1 inch = 16 chains General Map Collection