At the Clements Library:
Miscellaneous collection: Letter from N. G. Ingraham, ca. 1795.
Wilson papers: Letter from Nathan G. Ingraham to William Wilson, April 19, 1814.
The University of Michigan Library holds the following microform:
German, Obadiah. A Bill for the Relief of Nathaniel C. Ingraham, Alexander Phoenix, and William Nixsen, Junior. [Washington, s.n.], 1813.