|i.||Map based on section from Landforms of the United States, prepared at the Institute of Geographical Exploration, Harvard University, by Erwin Raisz. Colter's route shown by the heavy dotted line. Courtesy, Ginn and Company, Boston, Mass.|
|2.||Section from manuscript map by William Clark used as the basis for the engraved map in the 1814 edition of the HISTORY OF THE EXPEDITION UNDER THE COMMAND OF CAPTAINS LEWIS AND CLARK. Courtesy, Yale University Library, W. R. Coe Collection.|
|3.||Section from manuscript map by William Clark drawn in 1808 from George Drouillard's information. Courtesy, Missouri Historical Society, St. Louis, Mo.|
|4.||Section from engraved map issued with HISTORY OF THE EXPEDITION UNDER THE COMMAND OF CAPTAINS LEWIS AND CLARK, Philadelphia, 1814.|
Map I is reproduced on page xxxviii.
Maps 2, 3 and 4 will be found between pages 80 and 81.