| Kaggle | San Francisco | April 2010 |
| Kahr Arms | Pike County | 1995 |
| Kaiser Jeep | Toledo | 1953 |
| Kaiser Permanente | Oakland | 1945 |
| Kaltura | New York, New York City | 2006 |
| Kaplan International Languages | London | 1967 |
| Kayak.com | Stamford | 2004 |
| Keds | Rockford | 1916 |
| Kellanova | Chicago | February 19, 1906 |
| Kelvinator | — | 1914 |
| KeyBank | Cleveland | 1825 |
| Kingston Technology | Fountain Valley | 1987 |
| Kirby Company | Cleveland | 1914 |
| KLA Corporation | Milpitas | 1997 |
| Knight's Armament Company | Titusville | 1983 |
| Knoll | East Greenville | 1938 |
| Koch, Inc. | Wichita | 1940 |
| Kodak | Rochester, New York City | 1882 |
| Kohl's | Menomonee Falls | 1962 |
| Kohlberg Kravis Roberts | New York City | 1976 |
| Kraft Heinz | Pittsburgh | 2015 |
| Kumon | Osaka | 1958 |
| Language Creation Society | Garden Grove | 2007 |
| Las Vegas Sands | Las Vegas, Paradise | 1937 |
| Lay’s | — | 1934 |
| Lazard | New York City | July 12, 1848 |
| Lear Corporation | Southfield | 1917 |
| Leatherman | Portland | 1983 |
| Lehman Brothers | New York City | 1850 |
| Levi Strauss & Co. | San Francisco, Levi's Plaza | 1853 |
| Lexar | Milpitas | 1996 |
| Liberty Media | Douglas County, Colorado | 1991 |
| Liberty Mutual Insurance | Boston | 1912 |
| Lime | San Mateo | January 2017 |
| Line 6 | Calabasas | 1996 |
| Lionel Corporation | New York City | 1900 |
| Loews Corporation | New York City | 1946 |
| Logitech | Lausanne, Newark | October 2, 1981 |
| Lollapalooza | — | 1991 |
| Lonely Planet | Melbourne | 1972 |
| Lucasfilm Animation | San Francisco | May 12, 2003 |
| Lycoming | Williamsport | 1845 |
| M&T Bank | Buffalo | 1856 |
| Mack Trucks | Allentown, Greensboro | 1900 |
| Magpul | — | — |
| MakerBot Industries | New York City | January 20, 2009 |
| Marmot | Santa Rosa | 1974 |
| Marriott International | Bethesda | October 8, 1993 |