A biography of Joseph Nicollet, the brave & tireless explorer in 1838 & 1839 of the great northwestern triangle between the Missouri & the upper Mississippi rivers. Author Martha Coleman Bray has founded her very readable story on Nicollet's journals, survey documents, correspondence, & published writings. Trained as an astronomer in Paris, Nicollet came to America after the revolution of 1830. His early travels took him to the South & to the sources of the Mississippi River. He won the confidence of the leaders of the newly-founded Corps of Topographical Engineers (precursor of the U.S. Geological Survey) & with John Charles Fremont as his assistant, he led the first of two expeditions to the Northwest. The superb "Map of the Hydrographic Basin of the Upper Mississippi River, " which resulted from these expeditions, was basic to the further exploration of the West & is our only source of Indian names of landscape features of the region. The "Report" which accompanied the map reveals Nicollet's breadth of knowledge which brought him into the liveliest scientific circles of the U.S. He died in Washington in 1843. 300 illlus. & a fold-out map.