About one half of the correspondence consists of Marsh's drafts of reports to the Society in Scotland for Propagating Christian Knowledge, many of which are printed in Volume XV of the Wisconsin Historical Collections (pages 39-204). The remaining letters are from Marsh's former instructors at Andover, administrators in Indian work, or fellow missionaries, including: John Codman, Jeremiah Evarts, John A. Vinton, O.A. Taylor, Leonard Woods, all of Massachusetts; William T. Boutwell, Mrs. Julia E. Stevens, and Capt. S. Loomis, of Minnesota; Col. William Davenport, L.H. Loss, S.G. Spees of Illinois; Mrs. A.F. Davis and George N. Smith of Michigan; G.E. Stowe of Ohio; Dr. R.S. Satterlee of Florida; Jesse Voegler of Canada; and Sherman Hall, Stephen Peet, Moses Ordway, Jeremiah Porter, Dr. Charles McDougall, Charles Lord, William H. Spencer, William A. Niles, Levi Konkapot, and John W. Quinney, all of Wisconsin.
The collection also contains 58 small notebooks and journals which may be classified as follows: 17 miscellaneous notebooks in which Marsh jotted down memoranda on his reflections while a student, his missionary work at Maumee, Ohio, in the winter of 1829-1830, his eighteen years among the Stockbridge people with comments on Indian life, intemperance, archaeological remains, trips to neighboring settlements, modes of travel, visitors to the mission, work of fellow missionaries, letters written and received, orders for religious publications, expenses, Indian vocabularies, etc.; 12 journals which he kept while with the Stockbridge Indians, 1830-1848, at Statesburg and Stockbridge, a narrative of his religious work; 6 journals of an expedition to the Sauk and Fox Indians in the summer of 1834 made by way of the Fox-Wisconsin route and the Mississippi to Rock Island and thence up the Des Moines (also available on Micro 1016); and 23 journals, 1848-1856, of his preaching career in the Wisconsin pineries, with headquarters at Waupaca.
Letters to the American Board of Commissions for Foreign Missions are available only on microfilm (Micro 23). Originals of the letters on Micro 23 are at the United Church Board for World Ministries, Boston, Massachusetts. (These records may now be held at the Houghton Library, Harvard University.)
