| Alabama A & M University | historically black college or university, public educational institution of the United States, school, land-grant university, public university | — | 1875 |
| Alaska Railroad Corporation | national railway, Class II railroad | Anchorage | 1914 |
| Albemarle Corporation | business, enterprise, public company | Baton Rouge | 1994 |
| Alcon Entertainment | business, enterprise | Los Angeles | 1997 |
| Alcorn State University | historically black college or university, public educational institution of the United States, school, university, census-designated place in the United States, land-grant university | — | 1871 |
| Alexion Pharmaceuticals | business, enterprise, public company | Cheshire | 1992 |
| Allen-Bradley | business, public company | Milwaukee | 1903 |
| Alliant Techsystems | enterprise, public company, aerospace manufacturer | Arlington County | 1990 |
| Alliant University | private for-profit educational institution, university | San Diego | 2001 |
| Allison Engine Company | business | Indianapolis | 1915 |
| Allison Transmission | business, public company | Indianapolis | 1916 |
| Allstate | business, enterprise, public company | Northbrook | April 17, 1931 |
| Aloha Air Cargo | airline | Honolulu | 2008 |
| Altair Engineering | business, public company | Troy | 1985 |
| Altera | privately held company, business | San Jose | 1983 |
| Amaze Entertainment | video game developer, business | Kirkland | 1997 |
| Amazon Robotics | business | Massachusetts | January 1, 2003 |
| Amblin Partners | joint venture, company | Universal City | December 16, 2015 |
| AMC Global Media | public company | New York City | 1980 |
| AMC Theatres | cinema chain, business, public company | Kansas City | 1920 |
| Amdahl Corporation | business | Sunnyvale | October 19, 1970 |
| America West Airlines | airline | Tempe | 1981 |
| American Academy of Arts and Letters | academy of sciences, award | Washington Heights | 1899 |
| American Academy of Dramatic Arts | academy, drama school, private not-for-profit educational institution, organization | New York City | 1884 |
| American Airlines | airline, public company | Fort Worth | April 15, 1926 |
| American Automobile Association | nonprofit organization, business | Heathrow | 1902 |
| American Axle | business, enterprise, public company | Detroit | 1994 |
| American Bible Society | Bible society, nonprofit organization | Philadelphia | May 11, 1816 |
| American Broadcasting Company | radio network, television network, television station, film production company | New York City | May 15, 1943 |
| American Concrete Institute | organization, academic publisher | Farmington Hills | 1904 |
| American Economic Association | organization, open-access publisher, scientific society | Nashville | 1885 |
| American Express | multinational corporation, business, card association, public company | New York City | 1850 |
| American Film Institute | film organization, nonprofit organization, private not-for-profit educational institution, film school, educational organization | Los Angeles | 1967 |
| American Geophysical Union | nonprofit organization, open-access publisher, scientific society | Washington, D.C. | 1919 |
| American Girl | business | — | 1986 |
| American Heart Association | nonprofit organization, medical organization, open-access publisher | Dallas | June 10, 1924 |
| American Hockey League | professional sports league | — | 1936 |
| American Institute of Aeronautics and Astronautics | professional society, academic publisher | Reston | 1963 |
| American Institute of Physics | nonprofit organization, archives, publishing house, open-access publisher, scientific society | College Park | 1931 |
| American International Group | business, enterprise, public company | New York City | 1919 |
| American LaFrance | business, enterprise | Summerville | 1873 |
| American Library Association | nonprofit organization, open-access publisher, professional association, library association, academic publisher | Chicago | October 6, 1876 |
| American Line | transport company | Philadelphia | 1871 |
| American Megatrends | technology company, business, enterprise | Norcross | 1985 |
| American Psychological Association | regulatory college, nonprofit organization, publishing house, open-access publisher, professional association, school accreditor | Washington, D.C. | July 1892 |
| American Radiator Building | skyscraper, hotel | — | 1924 |
| American School of Classical Studies at Athens | educational institution, organization | — | 1881 |
| American Schools of Oriental Research | nonprofit organization, learned society, academic publisher | Boston | 1900 |