This is an interesting map showing the newly formed Dakota Territory as a huge unorganized area with its western boundary just beyond the Missouri River. Minnesota is more developed.  Interesting notation locates vast prairies said to be "...the great Hunting and Fighting Ground of Dakotah, Odjebwe, Assiniboin, Arikara, Minitarree and other Nations." The proposed Northern route of the Pacific Railroad is shown crossing the Dakota wilderness. Good detail overall with color coded counties shown as well.