- Massachusetts--Boston6
- Massachusetts--Wellesley2
- Massachusetts--Williamstown4
- Materia medica, Vegetable1
- Matthei, Bernardino1
- Medea, consort of Aegeus, King of Athens (Mythological character)1
- Medici, Alessandro de', 1510-15371
- Medici, Giovanni Giacomo de', marchese di Marignano, 1495-15551
- Medici, House of1
- Medicine4
- Medicine, Medieval1
- Meditations1
- Mediterranean Region1
- Mediterranean Sea1
- Mediterranean Sea--Adriatic Sea1
- Memory1
- Merchants1
- Meschiati, Giovanni1
- Middle Ages1
- Middle East--Jerusalem1