Issued with Warren's "Preliminary report of explorations in Nebraska and Dakota in the years 1855-'56-'57," originally printed in the appendixes to the Report of the Secretary of War, in the President's message and documents, Dec., 1858. "35th Congress, 1st Session. Printed by order of the U.S. Senate." "Explorations & surveys, War Dept., Hon. John B. Floyd, Secy. of War." Relief shown by hachures and spot elevations. Map shows routes of 20 exploration or survey parties. Dimensions: 118 x 84 centimeters