| California State University, Fullerton | public educational institution of the United States, university | Fullerton | 1957 |
| California State University, Los Angeles | public educational institution of the United States, university | Los Angeles | 1947 |
| California State University, Sacramento | public educational institution of the United States, university | Sacramento | 1947 |
| Caltex | brand, gas station chain | — | June 30, 1936 |
| Canadian Pacific Kansas City | holding company, railway company, public company | Calgary | April 14, 2023 |
| Cannondale Bicycle Corporation | bicycle manufacturer, brand, business | Bethel | 1971 |
| Canoo | business, automobile manufacturer, public company | Torrance | 2017 |
| Cape Air | airline | Hyannis | 1989 |
| Captain D's | fast food restaurant chain, business | Nashville | August 15, 1969 |
| Caravan Pictures | business | Santa Monica | 1992 |
| Cardinal Health | business, medical device company, enterprise, public company | Dublin | 1971 |
| Carfax | business, corporation | Centreville | 1984 |
| Caribou Coffee | café chain | Minneapolis, Brooklyn Center | 1992 |
| Carlo's Bake Shop | bakery | — | 1910 |
| Carlson Wagonlit Travel | business | Minneapolis | 1994 |
| Carnival Corporation | business, dual-listed company, public company, cruise line | Doral, Southampton, Florida, London, Miami | 1972 |
| Carroll University | liberal arts college, private not-for-profit educational institution, private university | Waukesha | 1846 |
| Carvana | car dealership, public company | Tempe | — |
| Castello di Amorosa | winery | — | April 2007 |
| Caterpillar Inc. | business, enterprise, public company | Irving | 1925 |
| CBS | radio network, television network | CBS Building | September 18, 1927 |
| CBS Corporation | business, enterprise, public company | CBS Building | November 30, 1997 |
| CBS News | television production company, specialty channel | CBS Broadcast Center | September 18, 1927 |
| Cecil H. Green Library | academic library, library building | Stanford | 1919 |
| Cedar Point | amusement park | — | 1870 |
| Cedars-Sinai Medical Center | educational institution, trauma centre, academic medical centre, non-profit hospital | Los Angeles | 1902 |
| Celestron | business, enterprise, company | Torrance | 1960 |
| Celgene | pharmaceutical company, business, enterprise, public company | Summit | 1986 |
| Cell Press | imprint, academic publisher | Cambridge | 1986 |
| Cencora | business, enterprise, public company | Chesterbrook | 2001 |
| Cengage Group | publishing house, business | Stamford | 2000 |
| Center for Open Science | scientific organization, 501(c)(3) organization, academic publisher | — | January 15, 2013 |
| Central Michigan University | public educational institution of the United States, public research university | Mount Pleasant | 1892 |
| Central Pacific Railroad | transport company | Sacramento | June 28, 1861 |
| Central Washington University | public educational institution of the United States, university | — | 1891 |
| Centre College | Colleges That Change Lives, private not-for-profit educational institution, liberal arts college in the United States | Danville | 1819 |
| Century 21 Real Estate | estate agent, business, enterprise | Madison | 1971 |
| Cerebras | business, company | Sunnyvale, San Francisco | 2016 |
| Champion Air | airline | Bloomington | 1995 |
| Chaosium | tabletop role-playing game publisher, board game publishing company, business | Hayward, Albany | October 31, 1975 |
| Chapman University | private not-for-profit educational institution, university | Orange | 1861 |
| Charles Scribner's Sons | publishing house | New York City | 1846 |
| Charter Oak State College | public educational institution of the United States, university | — | 1973 |
| Chateau Marmont | hotel | — | 1927 |
| Chautauqua Airlines | airline | Indianapolis | 1973 |
| Checkers and Rally's | fast food restaurant chain, dyad | — | 1986 |
| Chegg | dot-com company, technology company, public company | Santa Clara | 2005 |
| Chemical Abstracts Service | information system, publishing house | Columbus | 1907 |