| Jackson Guitars | Scottsdale | 1980 |
| Jacobs Solutions | Harwood Center | 1947 |
| Jacuzzi | Chino Hills | 1917 |
| Jakks Pacific | Malibu | 1995 |
| Jamba Juice | Frisco | 1990 |
| Jasc Software | Eden Prairie | 1990 |
| JBL | Northridge | 1946 |
| Jeep | Toledo | 1941 |
| Jimmy John's | Champaign | 1983 |
| John Hancock Insurance | Boston | 1862 |
| Jones Lang LaSalle | Chicago, Aon Center | 1783 |
| K-R-I-T Motor Car Company | Detroit | 1909 |
| Kaggle | São Francisco | abril 2010 |
| Kahr Arms | condado de Pike | 1995 |
| Kaiser Jeep | Toledo | 1953 |
| Kaltura | Nova Iorque, Nova Iorque | 2006 |
| Kate Spade New York | Nova Iorque | 1993 |
| KAYAK | Stamford | 2004 |
| Kaypro | San Diego | 1981 |
| Kel-Tec | Cocoa | 1991 |
| KeyBank | Cleveland | 1825 |
| Keysight | Santa Rosa | 2014 |
| Kimberly-Clark | Irving | 1928 |
| Kleiner Perkins | Menlo Park | 1972 |
| Kmart | Detroit | 1962 |
| Knight's Armament Company | Titusville | 1983 |
| Knoll | East Greenville | 1938 |
| Koch Industries | Wichita | 1940 |
| Kohlberg Kravis Roberts | Nova Iorque | 1976 |
| Koss Corporation | Milwaukee | 1953 |
| Kylie Cosmetics | Oxnard | 2014 |
| La Senza | Montreal | 1990 |
| Lattice Semiconductor | Portland, Hillsboro | 1983 |
| Lee | Kansas, Merriam | 1889 |
| Leidos | Reston | 1969 |
| Levi Strauss & Co. | São Francisco, Levi's Plaza | 1853 |
| Lexar | Milpitas | 1996 |
| Lexicon | Woodbury | 1971 |
| Liberty Media | Condado de Douglas, Colorado | 1991 |
| Liberty Mutual Group | Boston | 1912 |
| Linden Lab | São Francisco | 1999 |
| Line 6 | Calabasas | 1996 |
| LJN Toys | Nova Iorque | 1967 |
| Logitech | Lausana, Newark | 2 de outubro de 1981 |
| Lollapalooza | — | 1991 |
| Long Island Rail Road | Jamaica | 1834 |
| Long-Term Capital Management | Greenwich | 1994 |
| Lotus Software | Cambridge | 1982 |