| Cencora | Chesterbrook | 2001 |
| Cengage Group | Stamford | 2000 |
| Century 21 Real Estate | Madison | 1971 |
| Cerebras | Sunnyvale, San Francisco | 2016 |
| Chaosium | Hayward, Albany | October 31, 1975 |
| Chemical Bank | Midland, New York City | 1954 |
| Chikara | Philadelphia | 2002 |
| Chrome Holding Co. | South San Francisco | April 2006 |
| CHS Inc. | Inver Grove Heights | 1931 |
| Circuit City Stores | Richmond | 1984 |
| CIT Group | New York City | 1908 |
| Citibank | Sioux Falls, New York City | 1865 |
| Citizens Financial Group | Providence | 1954 |
| Citrix Systems | Fort Lauderdale | 1989 |
| Clinique Laboratories, LLC | New York | 1968 |
| CME Group | Chicago, London | July 12, 2007 |
| Codecademy | New York City | 2011 |
| CodeGear | Scotts Valley, California | 2006 |
| Coinbase | San Francisco | June 20, 2012 |
| Coldwell Banker | Cairo, Madison | August 27, 1906 |
| Colgate-Palmolive Company | New York City | 1806 |
| Colorado Fuel and Iron | Colorado | — |
| Colt's Manufacturing Company | West Hartford | 1855 |
| Columbia Sportswear Company | Cedar Mill | 1938 |
| Comcast | Philadelphia | June 28, 1963 |
| Comerica | Dallas | 1849 |
| Commonwealth Fusion Systems | Devens | 2018 |
| CommScope | Claremont | 1976 |
| Comodo Group | Clifton | 1998 |
| Comscore | Reston | 1999 |
| Concentrix | Fremont | 2004 |
| Control Data Corporation | Bloomington | 1957 |
| Converse | Boston | 1910 |
| Cord Automobile | United States | 1929 |
| CoreWeave | Roseland | 2017 |
| Corteva | Washington, D.C. | March 15, 2018 |
| Costco | Issaquah | 1983 |
| Coty | New York City | 1904 |
| CoverGirl | Maryland | 1961 |
| Cox Communications | Phoenix | 1962 |
| Crayola LLC | Forks Township | 1885 |
| Crosley | Cincinnati | 1937 |
| CrossFit | Santa Cruz | 2000 |
| CrowdStrike | Austin | August 29, 2011 |
| Crunchbase | San Francisco | July 2007 |
| Crystal Cruises | Los Angeles | 1988 |
| Culligan | Rosemont | 1936 |
| Currier and Ives | New York City | 1835 |