- 2 Astronomers
- 2 Astronomical charts
- 8 Astronomy
- 52 Asylums (welfare buildings)
- 1 At work yet (Sculpture)
- 1 Atco, New Jersey
- 1 Athanasian Creed
- 1 Athanasius, Saint, Patriarch of Alexandria, d. 373
- 3 Athena
- 6 Athenaeum Club (London, England)
- 8 Athenaeum of Philadelphia
- 7 Athenaeums
- 12 Athens, Greece
- 3 Athletic clubs
- 5 Athletic fields
- 1 Atkinson's Mill
- 3 Atlanta, Georgia
- 1 Atlantic Barrel Manufactury
- 6 Atlantic City, New Jersey
- 2 Atlantic Coast Seaman's Union
- 8 Atlantic County, New Jersey
- 1 Atlantic Dryer & Varnish Co.
- 4 Atlantic Knitting Mill (J. S. Jones)
- 1 Atlantic Petroleum Storage Company
- 4 Atlantic Refining Co.
- 1 Atlas Manufacturing Co.
- 3 Atlases
- 1 Atlee, Washington L. (Washington Lemuel), 1808-1878
- 2 Atmore & Son (Firm)
- 4 Atmore Mince Meat Factory
- 2 Attics (interior spaces)
- 1 Attorney General
- 5 Attributes (symbols)
- 1 Attucks, Crispus, d. 1770
- 1 Attwood, William, fl. 1836-1850
- 1 Aub, Hackenburg & Co.
- 1 Auburn Manufacturing Co.
- 18 Auburn, Indiana
- 4 Auction houses
- 5 Auctioneers
