PLSO The Oregon Surveyor May/June 2021

17 Professional Land Surveyors of Oregon | www.plso.org Featured Article line of sight. These maps were general- ly sketched on the ground or on animal skin and then copied in their journals or on map paper. One of the few surviving maps drawn by Lewis is a detailed sketch of the Great Bend of the Missouri River in the vicinity of the junction of the Missouri and Knife rivers in present western North Dakota. It was copied from an original drawn by David Thompson, an astronomer and surveyor employed by a fur trapping firm named the NorthWest Company. Thomp- son visited this area in 1798. His map also shows the number of warriors, houses, and tents of the Mandan and the Paw- nee Indian villages. A notation added by Thomas Jefferson provides information on the latitude and longitude. Another map associated with theMandan Indians is a map of the Yellowstone River. It was based on information provided to Clark by a Mandan chief named Shahaka [http://www.edgate.com/lewisandclark/ BIOs/BIO_Shahaka.html] or Big White fol- lowing his hunting trip to the Yellowstone River region of Wyoming in the winter of 1805. It is the first map to show this river and its tributaries. Most of the Indianmaps collected by Lew- is and Clark show areas west of the Rocky Mountains. Clarknoted inhis journal onOct. 18, 1805: “The Great Chief and one of the Chim-nâ pum nation drewme a Sketch of the Columbia [River] above and the tribes of his nation, living on the bank, and its waters, and the Tâpe têtt river which falls in 18 miles above on the westerly side.” Thismapwasoriginallydrawnwithapieceof coal on an Indian robe. It depicts theUpper Columbia and Yakima rivers in present- day southeastern Washington State, a region not explored by Lewis and Clark. This image is incorporated in Lewis and Clark’s printed map of 1814. Composite Maps of the West The final type of maps compiled on the trail were composite maps of the West. Two were prepared. These were compiled by Clark during the long winter camps at Fort Mandan (Oct. 1804–April 7,1805) and Fort Clatsop (Dec. 7, 1805–March 23,1806). Both cover the entire West from the Mis- sissippi River to the Pacific Coast. The Fort Mandan map is the first map of the West derived from personal obser- vations and measurements. It was based partly on the explorations of Lewis and Clark and partly on Indian information. The depiction of the lower Missouri River was taken from Clark’s finished traverse surveys and is quite accurately portrayed. The vast region to the west of Fort Man- dan and the Missouri River was derived from Indianmaps and verbal descriptions. The rivers shown are quite distorted be- cause of the Indians’ different concepts of space, time, and direction. Nevertheless, this information was ex- tremely valuable to the explorers. It provided Lewis and Clark with an im- provedmentalmapof theWest that helped them in planning the final leg of their journey. In one important aspect, how- ever, this map was both comforting and misleading. Based on information re- ceived from a Gros Ventres Indian, Clark showed a dotted line extending from the Mandan-Hidatsa villages to the Columbia River. This line was labeled “The war path of the Big Bellies Nation.” It showed that there was an existing Indian trail over the Rocky mountains that might be followed by Lewis and Clark. At the same time, the map showed that this trail passed over a single mountain range that suggested an easy crossing. The reality was quite different. The Lolo trail that the explorers followed over the Bitterroot mountains in modern day Ida- ho proved to be the most difficult part of the entire expedition. Instead of finding a low-lying single mountain ridge, they dis- covered numerous ranges of great height that extendednearly onehundredmiles. x