Account of an expedition from Pittsburgh to the Rocky Mountains : performed in the years 1819, 1820 : by order of the Hon. J.C. Calhoun, Secretary of War, under the command of Maj. S.H. Long, of the U.S. Top. Engineers / compiled from the notes of Major Long, Mr. T. Say, and other gentlemen of the party, by Edwin James, botanist and geologist to the Expedition.