The Kansas State Historical Society has an online searchable database of correspondence during William Clark’s tenure as the Superintendent, U.S. Office of Indian Affairs, Central Superintendency, St. Louis, and the tenures of others thereafter.
The database currently contains vols. 1-9, and vol. G–the only lettered volume in the series, which contains the last of Clark’s correspondence. It is an ongoing project, with more content regularly added.
The following microfilm of the Clark Papers is available for interlibrary loan: vols. 1-4 (reel no. MS 94); vols. 5-8 (reel no. MS 95); vols. 9-13 (reel no. MS 96); vols. 14-20 (reel no. MS 97); vols. 21-25 (reel no. MS 98); vols. 26-33 (reel no. MS 99).
Indian records include correspondence, 1813-1855; claims, 1807-1830; licenses and permits 1813-1825; descriptions, 1815-1817; journals, 1826-1835; property returns, 1840-1853; accounts, 1822-1853; and correspondence registers, 1837-1839, of the Missouri, Central, and St. Louis Superintendencies of Indian Affairs. The records contain information on the Indian emigration, treaties, the fur trade, claims, Indian education, roads, employees, meteorology, and steamboats. Indian agencies represented include the Osage, Sac & Fox, St. Peters, Upper Missouri River, and others; Indians represented include the Delaware, Fox, Ottawa, Sauk, Seneca, Shawnee, Sioux (195 results), and others.
The Chippewa are not listed on the front page as one of the searchable Native American nations, but I searched “Chippewa” and got 83 hits.