- Marie M. and Edith W. Smith Papers, 1783/18621
- Mary Ann Magnoni Sabbath notebook, 18361
- Mary Thedieck Ewald Papers, circa 1934-1990, 1934/19901
- Mary and Hannah Gibbons Papers, 1743/18901
- Materia Medica Notebook, 1840/18501
- Mathematics Notebook, 17991
- Matron's Circle of Mount Independence. Grange No. 482 (Falmouth, Me.), Minute Book, 1910/19131
- Medical Notebook, 18361
- Michael Kelly collection, 1840/18701
- Mildred Jackson Papers, 1938/19761
- Moncure Robinson Papers, 1787/18891
- Morton Genealogical Inquiries Collection, 1844/19601
- Morton Genealogy Collection, 1830/19781