- Arnott, Neil, 1788-18745
- Arthur, Robert, 1819-18801
- Asbury, Jacob Vale.1
- Ashton, Henry.1
- Ashwell, Samuel, 1798-18572
- Assalini, Paolo, 1759-1846?1
- Asylum for the Insane at Charlestown.1
- Asylum for the Relief of Persons Deprived of the Use of Their Reason.1
- Atkins, Dudley, 1798-18452
- Atlee, Edwin Augustus, 1776-18521
- Atlee, Washington L. (Washington Lemuel), 1808-18784
- Atticus.1
- Atwater, Caleb, 1778-18671
- Augusta State Hospital (Augusta, Me.)1
- Auzoux, Louis Thomas Jérôme, 1797-18802
- Averill, Charles.1
- Averill, Chester, 1804-18361
- Avery, S. W. (Stephen Waterman), 1800-18331
- Aydelott, B. P. (Benjamin Parham), 1795-18801
- Ayre, Joseph, 1781-18603