| IFixit | San Luis Obispo | 2003 |
| IGN | San Francisco | September 29, 1996 |
| Illinois Tool Works | Glenview | 1912 |
| ImageShack | Los Gatos | November 2003 |
| IMG | New York City | 1960 |
| Imgur | San Francisco | 2009 |
| Impossible Foods | Redwood City | 2011 |
| Incyte | Wilmington | 2001 |
| Indeed | Austin | November 2004 |
| InFocus | Tigard | 1986 |
| Infor Global Solutions | New York City | 2002 |
| Ingram Micro | Irvine | 1979 |
| InnoCentive | Waltham | 2001 |
| Inovio Pharmaceuticals | Plymouth Meeting | 1983 |
| Instacart | San Francisco | 2012 |
| Institute for Scientific Information | Philadelphia | 1960 |
| Intel | Santa Clara | July 18, 1968 |
| Intersil | Milpitas | 1967 |
| Invesco | Atlanta | 1935 |
| IQVIA Holdings, Inc. | Danbury, Durham | 2016 |
| Issuu | Palo Alto | 2007 |
| ITT Corporation | Stamford | 1920 |
| J. G. Brill Company | Philadelphia | 1868 |
| Jack Daniel's | Jack Daniel's Distillery | 1866 |
| Jacobs Engineering Group | Harwood Center | 1947 |
| Jakks Pacific | Malibu | 1995 |
| Jamba | Frisco | 1990 |
| JanSport | San Leandro | 1967 |
| Jasc Software | Eden Prairie | 1990 |
| JBL | Northridge | 1946 |
| Jeep | Toledo | 1941 |
| Jelly Belly | Fairfield | 1898 |
| Jet | — | — |
| Jimmy John's | Champaign | 1983 |
| John Hancock Insurance | Boston | 1862 |
| Jones Lang LaSalle | Chicago, Aon Center | 1783 |
| Juul | San Francisco | July 2017 |
| K-Swiss | Westlake Village | 1966 |
| Kahr Arms | Pike County | 1995 |
| Kayak.com | Stamford | 2004 |
| Kaypro | San Diego | 1981 |
| Kearney | Chicago | 1926 |
| Keds | Rockford | 1916 |
| Kel-Tec | Cocoa | 1991 |
| Kelvinator | — | 1914 |
| Keurig Dr Pepper | Burlington | 2018 |
| KeyBank | Cleveland | 1825 |
| Keystone Studios | Edendale | 1912 |