Book section introduces a manuscript map set consisting of thirty-nine plates that was made by William H. Hutton and J. Hudson Snowden during the summers of 1855 and 1856 under the direction of Lieutenant Gouverneur Kemble Warren. Warren's background as an accomplished member of the United States Army's Corps of Topographic Engineers is explained. Details of his assignment to map the Missouri River are also provided. The maps themselves are described and their symbols and notations are explained. Lastly, the significance of Warren's maps as well as their impact upon the history of the Missouri Valley region is described.