Entrance to Chicago harbor showing the state of the bar April 4th, 1854 before the dredging of the direct ship channel was commenced.
The soundings are in feet & tenths. Those expressed in small figures were made by Mr. Wm. Gamble, U.S. Agent on April 4th 1854. The 12 ft. curve is laid down from the soundings of Lt. Col. J.D. Graham made in April 1854 which are expressed in large figures. "Accompanying Lt. Col. J.D. Graham's report (no. 73) to the Chief Topographical Engineer, dated Chicago, April 29th 1855. Also referred to in the annual report (no. 116) from same to same, dated Chicago, December 31st 1855." "Map G. No. 11." 1 map; 54 x 77 cm
Gamble, William, Graham, J. D. (James Duncan), 1799-1865, and United States. Army. Corps of Topographical Engineers