- American Institute of Architects. New York Chapter., Committee on Civic Design and Development1
- American Institute of Mining Engineers. Meeting Halifax, N.S.) (18851
- American Institute of Planners2
- American Institute of Planners. New York Regional Chapter1
- American Institute of the City of New York3
- American Institute of the City of New York. Fair1
- American Institute of the City of New York. Fair New York, N.Y.) 18761
- American International Corporation1
- American Jewish Committee. New York Chapter1
- American Legion. Peter Minuit Post No. 1247 (Bronx County (N.Y.))1
- American Museum of Natural History3
- American Photo-Lithographic Company1
- American Print Works1
- American Scenic and Historic Preservation Society3
- American Sight Seeing Car and Coach Company1
- American Society for Colonizing the Free People of Colour of the United States1
- American Society of Civil Engineers4
- American Society of the City of New York, for the Encouragement of Domestic Manufactures1
- American Sunday-School Union3
- American Theatre Wing1
- American Tract Society1
- Ames, Fisher, 1758-18081
- Ammerman & Ford (Firm)1
- Anderson, Alexander, 1775-18702
- Anderson, James1
- Anderson, Martin Brewer, 1815-18901
- Andrew B. Graham Co1
- Andrews, Ebenezer Turrell, 1766-18511
- Andrews, G. H. 1816-18981
- Andrews, William Loring, 1837-19206
- Annand, Douglas, 1903-19761
- Anstice, Henry, 1841-19221
- Anthony, A. V. S. 1835-19061
- Anthony, Susan B. 1820-19061
- Anti-Protective Tariff League of Minnesota1
- Antin, Mary, 1881-19491
- Appel, Joseph H. 1873-19491
- Appleton Press1
- Appleton, Thomas Gold, 1812-18841
- Arber, Edward, 1836-19121
- Archer, J1
- Archer, James, active 1835-18601
- Architects' Renewal Committee in Harlem (New York, N.Y.)1
- Arden, Elizabeth, 1878-19661
- Arens, Egmont1
- Arkwright Club1
- Armstrong, Hamilton Fish, 1893-19731
- Arnold, Benedict, 1741-18011
- Arnold, Isaac N., 1815-18841
- Arnoux, William Henry, 1831-19072
- Arrowsmith, R. 1860-19281
- Art Commission of the City of New York1
- Art Interchange Press (New York)1
- Arthur Billings Hunt Collection (Columbia University. Libraries)1
- Arthur D. Little, Inc1
- Arthur, T. S. 1809-18851
- Ashburner, Charles A. 1854-18891
- Asher & Adams1
- Associated Factory Mutual Fire Insurances Companies1
- Association for the Benefit of Colored Orphans (New York, N.Y.)1