As stated on the upper left hand corner of the map, this map illustrates "the plan of the defences of the Western and North-Western Frontier, as proposed by Charles Gratiot, in his report of Oct. 31, 1837." The Frontier is at the western edge of the central Midwestern states: Iowa, Missouri, Arkansas, and Louisiana. The Frontier is further defined by the regions inhabited by various Native American tribes who encountered the US military.