Hennepin moved to Holland by the late 1690s, where he published Nouvelle découverte d’un très grand pays situé‚ dans l’Amérique entre le Nouveau Mexique et la mer Glaciale (Utrecht, 1697) and Nouveau voyage d’un pais plus grand que l’Europe (Utrecht, 1698). The former was published in English in 1698 as A New Discovery of a Vast Country in America and contained "A Map of a Large Country Newly Discovered." Because Hennepin was now free from the prohibitions of the French king, these books offered a new account of his explorations in which he claimed to be the first European to descend the Mississippi River. His accounts were sometimes fanciful and inaccurate and his claim of discovering the mouth of the Mississippi was refuted by Andrew Ellicott and others. However, his works were widely read and very influential in shaping views of North America.
Father Hennepin popularized the notion of an easy communication from the Missouri River system to waters flowing into the Pacific Ocean. "A Map of a Large Country Newly Discovered" locates the mouth of the Mississippi River ("Meschasipi") too far to the west. The source of the Missouri River ("Otenta R.") appears as a lake in the mountains and is close to the source of the Rio Grande ("River of Magdalen"). His map from the 1697 French edition (not shown) depicts another river originating close to the source of the Missouri; this Great River of the West is shown flowing into the Gulf of California. By locating the origin of these great rivers in close proximity in the mountains, Hennepin’s maps affirm the pyramidal height-of-land theory which dominated the geographic concepts of North America in the eighteenth century and had a major influence on the planning of the Lewis and Clark Expedition.
Thomas Jefferson owned first editions of all three of Hennepin’s works and consulted them in preparing his western treatise An Account of Louisiana, which he presented to Congress in November of 1803. In addition to the two maps on display, the exhibition also shows a first edition of Nouveau voyage (1698).