| A+E Global Media | business, enterprise | New York City | 1984 |
| A. O. Smith | business, public company | Milwaukee | 1889 |
| A. T. Cross Company | business, public company | Lincoln | 1846 |
| A.D. Vision | film production company | Houston | 1992 |
| Abbott-Detroit | automobile manufacturer | Detroit | 1909 |
| ABC Signature | television production company | Burbank | March 21, 1985 |
| ABCorp | business | Stamford | 1795 |
| Abercrombie & Fitch | business, clothing store chain, public company | New Albany | 1892 |
| ABKCO Records | record label, business | New York City | 1961 |
| Abrams Books | publishing house, book distributor, business | New York City | 1949 |
| Academia.edu | document repository, social networking service, website, academic publisher | San Francisco | 2008 |
| Academy of Art University | private for-profit educational institution, art academy, university | San Francisco | 1929 |
| Academy of Motion Picture Arts and Sciences | film academy | Beverly Hills | May 11, 1927 |
| ACCO Brands | business, public company | Lake Zurich | 1903 |
| Ace Hardware | organization, business | Oak Brook | 1924 |
| Acoustical Society of America | publishing house, scientific society | Melville | 1928 |
| Activision | video game publisher, video game developer, subsidiary company | Santa Monica | October 1, 1979 |
| Actors Studio | drama school | New York City | October 5, 1947 |
| Adelphi University | private not-for-profit educational institution, school, university, organization | — | 1896 |
| AdMob | software company, business | Mountain View | 2006 |
| Adscape | business | San Francisco | 2006 |
| Aeria Games | business | Berlin | 2006 |
| Aeronca | aerospace manufacturer | Cincinnati, Middletown | 1928 |
| Affliction Entertainment | business | Los Angeles | 2008 |
| Aflac | business, public company | Columbus | 1955 |
| Ageia | business | Santa Clara | 2002 |
| Ahwahnee Hotel | lodge | — | 1927 |
| AIGA | regulatory college, nonprofit organization, private press, professional association | New York City | 1914 |
| AIM alliance | joint venture, alliance | — | October 2, 1991 |
| Air Tractor | business | Olney | 1973 |
| Air University | staff college, university | — | 1946 |
| Air Wisconsin | airline | Appleton | August 23, 1965 |
| Airtight Games | video game developer | Redmond | 2004 |
| Akamai Technologies | business, enterprise, content delivery network, public company | Cambridge, Massachusetts | 1998 |
| 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 |
| American Society for Testing and Materials | standards organization, business, company, learned society | West Conshohocken | 1961 |
| American Society of Composers, Authors and Publishers | copyright collective, nonprofit organization, performing rights organization, business, company | United States, New York City | 1914 |
| American Society of Mechanical Engineers | engineering society, regulatory college, organization, academic publisher | New York City | 1880 |
| American Sociological Association | nonprofit organization, learned society, academic publisher | 1430 K Street | 1905 |
| American Tourister | brand, business | Rhode Island | 1933 |
| American Tower Corporation | business, enterprise, public company | Boston | 1995 |
| American Type Founders | type foundry, business | Elizabeth | 1892 |
| American University | research university, private not-for-profit educational institution, private university | — | 1893 |
| American Zoetrope | production company, film production company | San Francisco | 1969 |
| AmericanConnection | airline | Indianapolis | 2001 |
| Ameriprise Financial | business, enterprise, public company | Minneapolis | 1894 |
| Ameristar Jet Charter | airline | Dallas | 2000 |
| Ametek | public company | Berwyn | 1930 |
| Amkor Technology | service provider, business, enterprise, public company | Tempe | 1968 |
| Ampere Computing | fabless semiconductor manufacturer, business | Santa Clara | 2017 |
| AMR Corporation | business, enterprise | Fort Worth | October 1, 1982 |
| Amtrak | independent agency of the United States government, public transport network, railway company | Washington Union Station | May 1, 1971 |
| Ancestry.com Inc. | business, database | Lehi | 1983 |
| Angelo State University | public educational institution of the United States, university | San Angelo | 1928 |
| Anheuser-Busch | business, enterprise, public company | St. Louis | 1852 |
| Annapurna Interactive | video game publisher, company | Los Angeles | December 1, 2016 |
| Annapurna Pictures | film production company, entertainment company | Los Angeles | 2011 |
| Anthology Film Archives | cinematheque, movie theater, film archive | — | November 30, 1970 |
| Anti- | independent record label | Los Angeles | 1999 |
| Antioch College | Colleges That Change Lives, private not-for-profit educational institution, liberal arts college in the United States | — | 1850 |
| Apatow Productions | television production company, film production company | Los Angeles | 1999 |
| Apollo Global Management | business, private equity firm, enterprise, public company | Solow Building | 1990 |
| Apollo Group | business, enterprise, public company | Phoenix | 1973 |
| Apollo Theater | movie theater, nightclub, music venue | — | 1914 |
| Apple Inc. | corporation, technology company, business, enterprise, public company | Cupertino | April 1, 1976 |
| Apple Studios | production company, company | — | October 2019 |
| Arby's | fast food restaurant chain, business | Sandy Springs | 1964 |
| ARCO | oil company, business, gas station chain, enterprise | Los Angeles | 1966 |
| Arctic Cat | business, enterprise, public company | Plymouth | June 1960 |
| Arctic Coal Company | mining company | Boston | 1906 |
| Arista Networks | business, public company | Santa Clara | October 2004 |
| Arizona State University | public educational institution of the United States, university, open-access publisher | Tempe | 1885 |
| Armadillo Aerospace | privately held company | Mesquite | 2000 |
| ArmaLite | small arms manufacturing company | Geneseo | 1954 |
| Armand Hammer United World College of the American West | boarding school, academic institution | Montezuma | 1982 |
| Arris Group | business, enterprise, public company | Suwanee | 1995 |
| Arrow Air | airline | — | 1947 |
| Arrow Electronics | business, public company | Englewood | 1935 |
| Artforum | publishing house, magazine | New York City | June 1962 |
| Arthur J. Gallagher & Co. | business, public company | Itasca | 1927 |
| Ashland Inc. | business, enterprise, public company | Covington | 1924 |
| Ashton-Tate | business, enterprise | Torrance | August 1980 |
| ASM International | engineering society, publishing house, organization | ASM Headquarters and Geodesic Dome | 1913 |
| Association for Computing Machinery | regulatory college, publishing house, organization, open-access publisher, scientific society, learned society | New York City | September 15, 1947 |
| Association for the Advancement of Artificial Intelligence | regulatory college, publishing house, scientific society | Palo Alto | 1979 |
| Astronomical Society of the Pacific | organization, academic publisher | — | 1889 |
| Astrophysics Data System | bibliographic database, data library, open-access repository | — | 1992 |
| AT&T | telecommunications company, business, enterprise, public company | Dallas | October 5, 1983 |
| Atari Corporation | video game publisher, technology company, business | Sunnyvale | July 2, 1984 |
| Atari, Inc. | video game publisher, video game developer | New York City | February 1993 |
| Atari, Inc. | video game publisher | New York City | February 1993 |
| Atlas Obscura | publishing house, brand, online encyclopedia, database | Greenpoint | 2009 |
| Au Bon Pain | business | Boston | 1978 |
| Auburn Automobile | business | Auburn | 1900 |
| Augusta National Golf Club | golf course, golf club, business | — | 1930 |
| Aurora University | private not-for-profit educational institution, university | Aurora | 1893 |
| Austin Peay State University | public educational institution of the United States, university | — | 1927 |
| Autocar Company | business | Hagerstown | 1897 |
| Automatic Data Processing | software company, business, enterprise, public company, accounting software | Roseland | 1949 |
| Avalon Hill | tabletop role-playing game publisher, board game publishing company | Baltimore, Renton | 1958 |
| Avatar Press | comics publishing company, book publisher, business, enterprise | Rantoul | 1996 |
| Avid Technology | business, enterprise, public company | Burlington | 1987 |
| Avnet | business, public company | Phoenix | 1921 |
| Awty International School | school, private school | — | 1956 |
| Axios | news website, business | Arlington County | 2017 |
| Aéropostale | clothing store chain, public company | New York City | 1973 |