- Margaret M. MacGill Genealogy Collection (MS254), 201887
- Marguerite More Collection (MS246), 1931/197124
- Mary Crawford Powell Collection (MS236), 19871
- Mary Louisa Slacum Benham Papers (MS062), 1802/188423
- Mary Powell Scott Papers (MS411), 1937/19392
- May Family Papers (MS233), 1846/194932
- McKenney-Mills Collection (MS413), 2000159
- McKnight, Piercy, and Jacobs Collection (MS051), 1792/19731
- Milton Penn Collection (MS267), 1794/189326
- Mollie Somerville Collection (MS156), 1966/19701
- Montgomery Dent Corse Papers (MS065), 1846/198217
- Mt. Vernon Cotton Factory Collection (MS097), 1866/18759