| 20th Century Studios Home Entertainment | Century City, Los Angeles | 1976 |
| 20th Television Animation | Los Angeles | May 19, 1999 |
| 3D Systems | Rock Hill | 1986 |
| 3dfx Interactive | San Jose | 1994 |
| 3M | Maplewood | 1902 |
| 7-Eleven | Dallas, Irving | 1927 |
| A+E Global Media | New York City | 1984 |
| A. O. Smith | Milwaukee | 1889 |
| A. T. Cross Company | Lincoln | 1846 |
| ABCorp | Stamford | 1795 |
| Abercrombie & Fitch | New Albany | 1892 |
| ABKCO Records | New York City | 1961 |
| Abrams Books | New York City | 1949 |
| ACCO Brands | Lake Zurich | 1903 |
| Ace Hardware | Oak Brook | 1924 |
| AdMob | Mountain View | 2006 |
| Adscape | San Francisco | 2006 |
| Aeria Games | Berlin | 2006 |
| Affliction Entertainment | Los Angeles | 2008 |
| Aflac | Columbus | 1955 |
| Ageia | Santa Clara | 2002 |
| Air Tractor | Olney | 1973 |
| Akamai Technologies | Cambridge, Massachusetts | 1998 |
| Albemarle Corporation | Baton Rouge | 1994 |
| Alcon Entertainment | Los Angeles | 1997 |
| Alexion Pharmaceuticals | Cheshire | 1992 |
| Allen-Bradley | Milwaukee | 1903 |
| Allison Engine Company | Indianapolis | 1915 |
| Allison Transmission | Indianapolis | 1916 |
| Allstate | Northbrook | April 17, 1931 |
| Altair Engineering | Troy | 1985 |
| Altera | San Jose | 1983 |
| Amaze Entertainment | Kirkland | 1997 |
| Amazon Robotics | Massachusetts | January 1, 2003 |
| AMC Theatres | Kansas City | 1920 |
| Amdahl Corporation | Sunnyvale | October 19, 1970 |
| American Automobile Association | Heathrow | 1902 |
| American Axle | Detroit | 1994 |
| American Express | New York City | 1850 |
| American Girl | — | 1986 |
| American International Group | New York City | 1919 |
| American LaFrance | Summerville | 1873 |
| American Megatrends | Norcross | 1985 |
| American Society for Testing and Materials | West Conshohocken | 1961 |
| American Society of Composers, Authors and Publishers | United States, New York City | 1914 |
| American Tourister | Rhode Island | 1933 |
| American Tower Corporation | Boston | 1995 |
| American Type Founders | Elizabeth | 1892 |