- Allin, William1
- Allington & Curtis Mfg. Co.2
- Allione, Costanzo1
- Allison, Graham1
- Allou Associates1
- Allsteel, Inc.5
- Allyn & Blanchard1
- Allyn House1
- Allyn, Blanchard & Latimer1
- Alman & Co.5
- Almar Construction Corp.1
- Alna Realty Corp.1
- Alonge, Ray1
- Aloni, Shulamit, 1927-20141
- Alonso, Odón, 1925-20111
- Alpark Realty Corp.1
- Alperin, Matt2
- Alpern, Andrew1
- Alpern, Sara, 1942-1
- Alpert, Stu1
- Alret Realty Corp.1
- Alsam Realty Corp.1
- Alsberg, Carl, 1877-19403
- Alsen, Olle1
- Alson Co.4
- Alson Trading Co.1
- Alsop, John, 1724-17943
- Alsop, Joseph, 1910-19892
- Alsop, Marin1
- Alter, Gerald M1
- Alter, Robert1
- Alter-Ciné, Inc.2
- Altham, Keith1
- Althouse Bros. Real Estate1
- Altier, Charles1
- Altman, Dorothy1
- Altman, Dorothy (Radio producer)1
- Altmeyer, Arthur J. (Arthur Joseph), 1891-19721
- Aluminum Novelty Works1
- Alumni Federation of Columbia University2
- Alva, Margaret, 1942-1
- Alvarez, Celia2
- Alvarez, José Alberto1
- Alves, Rubem A., 1933-20141
- Alvin H. Perlmutter, Inc.3
- Alvord, Corydon A., approximately 1812-18741
- Amacher, Maryanne1
- Amacker, Robert, 1944-1
- Amal Realty1
- Amalgamated Clothing Workers of America1
- Amalgamated Meat Cutters and Butcher Workmen of North America, AFL-CIO3
- Amato, Bruno1
- Amaya Distribution (Firm)1
- Amaya, Mario2
- Ambali, Folashade1
- Ambassador's Maid (Musical group)1
- Ambrica Productions3
- Ambrose E. Barnes & Bro.1
- Ambrose, George1
- Amen, John Harlan, 1898-19601