| AbbVie | biopharmaceutical company, business, public company | North Chicago | April 10, 2012 |
| ABC Family Worldwide | television production company, business | Burbank | 1990 |
| ABCorp | business | Stamford | 1795 |
| Abercrombie & Fitch | business, clothing store chain, public company | New Albany | 1892 |
| AbioMed | business, public company | Danvers | 1981 |
| About.com | media company, website | — | April 21, 1997 |
| 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 |
| Academy of Natural Sciences of Drexel University | nonprofit organization, natural history museum, academy of sciences, learned society | Philadelphia | 1812 |
| Ace Hardware | organization, business | Oak Brook | 1924 |
| Activision | video game publisher, video game developer, subsidiary company | Santa Monica | October 1, 1979 |
| Acxiom | business, public company | Wilmington, Conway | 2018 |
| Adaptec | business, enterprise | Sunnyvale | 1981 |
| Adscape | business | San Francisco | 2006 |
| Advance Auto Parts | car parts shop chain, business, public company | Roanoke | 1932 |
| Aeronca | aerospace manufacturer | Cincinnati, Middletown | 1928 |
| Affliction Entertainment | business | Los Angeles | 2008 |
| Aflac | business, public company | Columbus | 1955 |
| Ahwahnee Hotel | lodge | — | 1927 |
| AIGA | regulatory college, nonprofit organization, private press, professional association | New York City | 1914 |
| Air Cargo Carriers | airline | Milwaukee | 1986 |
| Air Force Institute of Technology | staff college, engineering education | — | 1919 |
| Air Wisconsin | airline | Appleton | August 23, 1965 |
| Airbnb | website, business, hotel booking website, enterprise, public company | San Francisco | 2008 |
| Airstream | brand, business | Jackson Center | 1931 |
| Airtable | spreadsheet, website, business | San Francisco | 2012 |
| Airtight Games | video game developer | Redmond | 2004 |
| AirTran Airways | airline | Dallas | 1993 |
| AK Press | book publisher, small press | Chico | 1987 |
| 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 |
| Alabama State University | public educational institution of the United States, school, public university | — | 1867 |
| Alamo Rent a Car | business | Clayton | 1974 |
| Albert Einstein College of Medicine | university, organization | — | 1955 |
| Albertsons | supermarket chain, business, enterprise, public company | Boise | 1939 |
| Aldi | supermarket chain, brand name | Essen, Mülheim an der Ruhr, Batavia | 1946 |
| Aldus | business | Seattle | February 1, 1984 |
| Alembic Inc | privately held company | Santa Rosa | 1969 |
| Alexion Pharmaceuticals | business, enterprise, public company | Cheshire | 1992 |
| Allegheny College | Colleges That Change Lives, private not-for-profit educational institution, liberal arts college in the United States | — | April 1815 |
| AllianceBernstein | business, enterprise, public company | Nashville | 1967 |
| Alliant University | private for-profit educational institution, university | San Diego | 2001 |
| Allis-Chalmers | business | Milwaukee | 1901 |
| Allison Engine Company | business | Indianapolis | 1915 |
| Aloha Air Cargo | airline | Honolulu | 2008 |
| Aloha Airlines | airline | Honolulu | 1946 |
| Altair Engineering | business, public company | Troy | 1985 |
| Altria | multinational corporation, public company | Richmond | 1985 |
| Amaze Entertainment | video game developer, business | Kirkland | 1997 |
| Amazon | very large online platform, business, enterprise, public company | Seattle | July 5, 1994 |
| Amazon Air | virtual airline | — | November 1, 2015 |
| Amazon Go | retail chain | Seattle | December 5, 2016 |
| Amazon Lab126 | business | Cupertino | 2004 |
| Amazon MGM Studios | film production company, film distributor | Culver City | 2010 |
| Amazon Robotics | business | Massachusetts | January 1, 2003 |
| Amblin Entertainment | television production company, animation studio, film production company | Universal City | 1981 |
| Amblin Partners | joint venture, company | Universal City | December 16, 2015 |
| Amblin Television | business | Universal City | July 31, 1984 |
| Ameren | holding company, public company | St. Louis | 1997 |
| America West Airlines | airline | Tempe | 1981 |
| American Academy in Rome | nonprofit organization, educational institution, research center | Rome, New York City | 1894 |
| American Academy of Arts and Sciences | nonprofit organization, learned society, academic publisher | Cambridge | May 4, 1780 |
| American Academy of Dramatic Arts | academy, drama school, private not-for-profit educational institution, organization | New York City | 1884 |
| American Antiquarian Society | research library, nonprofit organization, historical society, learned society | Worcester | 1812 |
| American Association for the Advancement of Science | nonprofit organization, open-access publisher, international organization, academic publisher | Washington, D.C. | September 20, 1848 |
| American Association of Physics Teachers | publishing house, scientific society | — | December 31, 1930 |
| 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 Bridge Company | business | Coraopolis | 1900 |
| American Cyanamid | business | Wayne | 1907 |
| American Economic Association | organization, open-access publisher, scientific society | Nashville | 1885 |
| American Electric Power | holding company, business, enterprise, public company | Columbus, Jersey City | August 1927 |
| American Express | multinational corporation, business, card association, public company | New York City | 1850 |
| American Geographical Society | publishing house, geographical society | Manhattan | 1851 |
| American Heart Association | nonprofit organization, medical organization, open-access publisher | Dallas | June 10, 1924 |
| American Hockey League | professional sports league | — | 1936 |
| 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 Library Association | nonprofit organization, open-access publisher, professional association, library association, academic publisher | Chicago | October 6, 1876 |
| American Line | transport company | Philadelphia | 1871 |
| American Locomotive Company | business | Schenectady, New York City | June 24, 1901 |
| American Motors Corporation | automobile manufacturer | Kenosha | 1954 |
| American Psychological Association | regulatory college, nonprofit organization, publishing house, open-access publisher, professional association, school accreditor | Washington, D.C. | July 1892 |
| American Sociological Association | nonprofit organization, learned society, academic publisher | 1430 K Street | 1905 |
| American Statistical Association | production company, nonprofit organization, open-access publisher, scientific society | Boston | November 27, 1839 |
| American Tourister | brand, business | Rhode Island | 1933 |
| American Type Founders | type foundry, business | Elizabeth | 1892 |
| American University | research university, private not-for-profit educational institution, private university | — | 1893 |
| American University of the Caribbean | university | Coral Gables | 1978 |
| American Wrestling Association | business, enterprise | Minneapolis | 1960 |
| American Zoetrope | production company, film production company | San Francisco | 1969 |
| Ametek | public company | Berwyn | 1930 |
| Amgen | biopharmaceutical company, business, enterprise, public company | Thousand Oaks | 1980 |
| Amkor Technology | service provider, business, enterprise, public company | Tempe | 1968 |
| Amoco | oil company | Chicago | 1889 |
| Amplifon | public company | Milan | 1950 |
| Amway | multi-level marketing company | Michigan | November 9, 1959 |
| Analog Devices | business, enterprise, public company | Norwood | 1965 |
| Anchor Brewing Company | brewery, business | San Francisco | 1896 |
| AND1 | manufacturing company, subsidiary company | Aliso Viejo | 1993 |
| Angel Studios | production company, streaming media, video streaming service | Provo | March 25, 2021 |
| Angelo State University | public educational institution of the United States, university | San Angelo | 1928 |
| Aniplex of America | business, enterprise | Santa Monica | 2005 |
| Annapurna Interactive | video game publisher, company | Los Angeles | December 1, 2016 |
| Annual Reviews | nonprofit organization, publishing house, academic publisher | San Mateo, Palo Alto | 1932 |
| Anonymous Content | television production company, film production company | Culver City | 1999 |
| Anschutz Entertainment Group | business | Los Angeles | — |
| Anthology Film Archives | cinematheque, movie theater, film archive | — | November 30, 1970 |
| Anthropic | technology company, business, benefit corporation | San Francisco | January 26, 2021 |
| Anti- | independent record label | Los Angeles | 1999 |
| APC by Schneider Electric | trademark, business, enterprise | West Kingston | 1981 |
| Apollo Computer | business | Chelmsford | 1980 |
| Apollo Group | business, enterprise, public company | Phoenix | 1973 |
| Appalachian State University | public educational institution of the United States, university | Boone | 1899 |
| Apple Store | shop, electronics store chain | — | May 19, 2001 |
| Applebee's | franchisor, restaurant chain | Kansas City | November 19, 1980 |
| Archegos Capital Management | business | Manhattan | October 9, 2001 |
| Archie Comics | comics publishing company, book publisher, business | New York, Pelham | 1939 |
| Arctic Coal Company | mining company | Boston | 1906 |
| ArenaNet | video game developer, business, enterprise | Bellevue | 2000 |
| Aria Resort and Casino | skyscraper, casino, hotel | — | 2009 |
| Arista Networks | business, public company | Santa Clara | October 2004 |
| Arkham House | book publisher, publishing house | Sauk City | 1939 |
| ArmaLite | small arms manufacturing company | Geneseo | 1954 |
| ARP Instruments, Inc. | business, musical instrument manufacturing company | United States | 1969 |
| Arquitectonica | interior decoration firm, architectural firm | Miami | 1977 |
| Arrow Air | airline | — | 1947 |
| Art Institute of Chicago | nonprofit organization, educational institution, art museum | Chicago | 1879 |
| Art Students League of New York | arts venue, art academy | 57th Street | 1875 |
| Arthur D. Little | management consulting company | Brussels metropolitan area | 1886 |
| Arthur J. Gallagher & Co. | business, public company | Itasca | 1927 |
| ArXiv | bibliographic database, website, preprint server, disciplinary repository, open science tool, online database | — | August 14, 1991 |
| Ashland Inc. | business, enterprise, public company | Covington | 1924 |
| ASICS | multinational corporation, public company | Kobe | 1949 |
| ASM International | engineering society, publishing house, organization | ASM Headquarters and Geodesic Dome | 1913 |
| Aspen Music Festival and School | annual event, nonprofit organization, conservatory, music festival | — | 1949 |
| Aspyr | video game publisher, video game developer | Austin | 1996 |
| Association for Computational Linguistics | publishing house, open-access publisher, learned society | Stroudsburg | 1962 |
| Association for Computing Machinery | regulatory college, publishing house, organization, open-access publisher, scientific society, learned society | New York City | September 15, 1947 |
| AST Research | business | Irvine | 1980 |
| AT&T Corporation | concern, business, enterprise | Boston, Texas, 550 Madison Avenue, Dallas, United States, 195 Broadway, New York City, Bedminster | March 3, 1885 |
| AT&T Mobility | mobile network operator, telecommunications company | Atlanta | 2001 |
| ATA Airlines | airline | Indianapolis | 1973 |
| Atari Games | video game publisher, video game developer | Milpitas | July 1984 |
| Atari, Inc. | video game publisher, video game developer | New York City | February 1993 |
| Atari, Inc. | video game publisher | New York City | February 1993 |
| Atchison, Topeka and Santa Fe Railway | railway company | Chicago | 1895 |
| Atlantic Southeast Airlines | airline | Hartsfield–Jackson Atlanta International Airport | 1979 |
| Atlas Obscura | publishing house, brand, online encyclopedia, database | Greenpoint | 2009 |
| Au Bon Pain | business | Boston | 1978 |
| Audiomachine | musical group, enterprise | Los Angeles | August 20, 2005 |
| Augusta National Golf Club | golf course, golf club, business | — | 1930 |
| Aurora University | private not-for-profit educational institution, university | Aurora | 1893 |
| AutoZone | car parts shop chain, public company | Memphis | 1979 |
| Avatar Press | comics publishing company, book publisher, business, enterprise | Rantoul | 1996 |
| Avery Dennison | public company | Glendale | 1935 |
| Avid Audio | business, subsidiary company | Daly City | 1984 |
| Avis Budget Group | business, public company | Parsippany-Troy Hills | 2006 |
| Awty International School | school, private school | — | 1956 |
| Axios | news website, business | Arlington County | 2017 |
| Azusa Pacific University | church college, private not-for-profit educational institution, seminary, university | — | 1899 |
| Aéropostale | clothing store chain, public company | New York City | 1973 |