| C. F. Martin & Company | business | Nazareth | 1833 |
| C. H. Robinson Worldwide | business, public company | Eden Prairie | 1905 |
| Cadillac | automobile manufacturer | Detroit | 1902 |
| Caesars Entertainment Corporation | business, enterprise | Las Vegas, Paradise | 1937 |
| California Academy of Sciences | planetarium, nonprofit organization, natural history museum, public aquarium, academy of sciences, learned society | San Francisco | 1853 |
| California Baptist University | church college, private not-for-profit educational institution, university | — | 1950 |
| California Institute of the Arts | private not-for-profit educational institution, film school, art academy, private university | — | 1961 |
| California Lutheran University | private not-for-profit educational institution, private university | Thousand Oaks | 1959 |
| California State Polytechnic University, Humboldt | public educational institution of the United States, university | — | 1913 |
| California State University, Bakersfield | public educational institution of the United States, university | Bakersfield | 1965 |
| California State University, Chico | public educational institution of the United States, public university | Chico | 1887 |
| California State University, Dominguez Hills | public educational institution of the United States, university | Carson | 1960 |
| California State University, East Bay | public educational institution of the United States, university | Hayward | 1957 |
| California State University, Fresno | public educational institution of the United States, university | Fresno | 1911 |
| 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 |
| Chemical Bank | business | Midland, New York City | 1954 |
| Chevrolet | car brand, automobile manufacturer | Detroit | November 3, 1911 |
| Chicago Public Schools | school district in the United States | Chicago | — |
| Chicago The Musical Ambassador Theater | Broadway theatre, theatre building, movie theater | — | February 11, 1921 |
| Chicago, Burlington and Quincy Railroad | railway company | Chicago | 1856 |
| Chick-fil-A | fast food restaurant chain | Georgia | 1946 |
| Chikara | business, professional wrestling promotion | Philadelphia | 2002 |
| Choate Rosemary Hall | boarding school, organization | Wallingford | 1890 |
| Christie's | educational institution, organization, auction house | New York City, London | 1766 |
| Chrome Holding Co. | business, enterprise | South San Francisco | April 2006 |
| Chronicle Books | book publisher, publishing house | San Francisco | 1967 |
| CHS Inc. | business, gas station chain, public company | Inver Grove Heights | 1931 |
| Chuck E. Cheese | indoor play space, restaurant chain, pizzeria chain, public company | Irving | May 17, 1977 |
| Church's Texas Chicken | fast food restaurant chain, restaurant chain | Sandy Springs | April 17, 1952 |
| Cinemark | cinema chain, public company | Plano | 1984 |
| Cinematronics | video game developer | El Cajon | 1975 |
| Cinemaware | video game publisher, video game developer | Burlingame | 1986 |
| Circuit City Stores | business, enterprise | Richmond | 1984 |
| Cirrus Aircraft Corporation | aerospace manufacturer | Duluth | 1984 |
| CIT Group | business, public company | New York City | 1908 |
| Citibank | bank, business, financial institution, credit institution | Sioux Falls, New York City | 1865 |
| Citizens Financial Group | bank, business, public company | Providence | 1954 |
| Citrix Systems | software company, business, enterprise, public company | Fort Lauderdale | 1989 |
| City University of New York | state university system, state agency of New York, urban university, public university | New York City | 1961 |
| Claremont Graduate University | private not-for-profit educational institution, private university | — | 1925 |
| Clark Atlanta University | historically black college or university, private not-for-profit educational institution, private university | — | September 19, 1865 |
| Clinique Laboratories, LLC | cosmetics, business, subsidiary company | New York | 1968 |
| Clinton Presidential Center | Presidential libraries system, museum | — | 2004 |
| Cloudflare | technology company, online service, content delivery network, public company | San Francisco | July 17, 2009 |
| ClubJenna | television production company, pornographic film studio | Scottsdale | 2000 |
| CME Group | stock exchange, business, enterprise, public company | Chicago, London | July 12, 2007 |
| Codecademy | open educational resource, Virtual learning environment, website, business | New York City | 2011 |
| CodeGear | business, enterprise | Scotts Valley, California | 2006 |
| Cognizant Technology Solutions | technology company, enterprise, public company | Teaneck | 1994 |
| Coinbase | cryptocurrency exchange, digital currency exchanger, business, public company, payment system | San Francisco | June 20, 2012 |
| Colby College | private not-for-profit educational institution, liberal arts college in the United States | Waterville | 1813 |
| Coldwell Banker | business, enterprise | Cairo, Madison | August 27, 1906 |
| Colgan Air | regional airline | Memphis | 1991 |
| Colgate-Palmolive Company | business, public company | New York City | 1806 |
| College of Charleston | liberal arts college, public educational institution of the United States, university | — | 1770 |
| College of the Holy Cross | liberal arts college, private not-for-profit educational institution, university | Worcester | 1843 |
| College of William & Mary | public educational institution of the United States, public research university | Williamsburg | 1693 |
| College of Wooster | liberal arts college, college, Colleges That Change Lives, private not-for-profit educational institution | Wooster | 1866 |
| Collins Aerospace | defense contractor, aerospace manufacturer | Charlotte | 2018 |
| Colorado College | liberal arts college, private not-for-profit educational institution | Colorado Springs | 1874 |
| Colorado Fuel and Iron | business | Colorado | — |
| Colorado State University | public educational institution of the United States, land-grant university, public research university | — | 1870 |
| Colt's Manufacturing Company | business, subsidiary company, enterprise | West Hartford | 1855 |
| Columbia College | college | — | 1754 |
| Columbia Pictures | film production company, film distributor | United States, Culver City | 1918 |
| Columbia Sportswear Company | business, enterprise, brick and mortar, public company | Cedar Mill | 1938 |
| Columbia University Press | book publisher, nonprofit organization, university press | New York City | 1893 |
| Columbia University Vagelos College of Physicians and Surgeons | graduate school, university, medical school | New York City | 1767 |
| Comcast | telecommunications company, business, enterprise, public company | Philadelphia | June 28, 1963 |
| Comerica | bank, business, financial institution, credit institution, public company | Dallas | 1849 |
| Commonwealth Fusion Systems | business | Devens | 2018 |
| CommScope | business, public company | Claremont | 1976 |
| Comodo Group | business, enterprise | Clifton | 1998 |
| Comscore | website, business, public company | Reston | 1999 |
| Concentrix | business | Fremont | 2004 |
| Condé Nast | publishing house | One World Trade Center | 1909 |
| Conoco | oil company, defunct organization | Houston | 1875 |
| Conrail | railway company | Philadelphia | April 1, 1976 |
| Constellation Energy | public company | Baltimore | 1999 |
| Continental Micronesia | airline | Tamuning | 1968 |
| Control Data Corporation | business, enterprise | Bloomington | 1957 |
| Converse | brand, business | Boston | 1910 |
| Cord Automobile | business | United States | 1929 |
| CoreWeave | business, enterprise | Roseland | 2017 |
| Cornell Law School | law school | — | 1887 |
| Cornell University | research university, private not-for-profit educational institution, land-grant university, sun grant institution, private university | Ithaca | 1865 |
| Corteva | business, public company | Washington, D.C. | March 15, 2018 |
| Cosmopolitan of Las Vegas | casino, hotel | — | April 2004 |
| Costco | business, retail chain, enterprise, public company | Issaquah | 1983 |
| Coty | business, enterprise, public company | New York City | 1904 |
| Council on Vertical Urbanism | publishing house, organization | Illinois Institute of Technology | 1969 |
| Courant Institute School of Mathematics, Computing, and Data Science | academic institute, faculty, higher education institution, organization | — | 1935 |
| CoverGirl | brand, business | Maryland | 1961 |
| Cox Communications | internet service provider, business | Phoenix | 1962 |
| Cox Enterprises | enterprise | Atlanta | 1898 |
| Cracker Barrel | restaurant chain, public company | Lebanon | September 19, 1969 |
| Crave Entertainment | video game developer | Newport Beach | 1997 |
| Cray | public company | Seattle | 1972 |
| Crayola LLC | business, enterprise | Forks Township | 1885 |
| Creative Artists Agency | talent agency, company | Century City | 1975 |
| Creative Commons | nonprofit organization, publishing house, author | Mountain View | January 15, 2001 |
| Creighton University | private not-for-profit educational institution, university, open-access publisher | Omaha | 1878 |
| Crocs, Inc. | retail chain, brick and mortar, public company | Longmont | 2002 |
| Crosley | business, automobile manufacturer | Cincinnati | 1937 |
| CrossFit | hobby, business | Santa Cruz | 2000 |
| CrowdStrike | business, public company | Austin | August 29, 2011 |
| Crunchbase | data set, website, business, online database | San Francisco | July 2007 |
| Crunchyroll | application software, video streaming service, Internet audio-visual programming service provider, mobile app, streaming service, Internet television | San Francisco | May 14, 2006 |
| Cryptic Studios | video game developer | Los Gatos | June 2000 |
| Crystal Cruises | business, cruise line | Los Angeles | 1988 |
| Culligan | business | Rosemont | 1936 |
| Currier and Ives | male duo, business | New York City | 1835 |
| Curtiss-Wright | holding company, business, public company, aerospace manufacturer | Charlotte | 1929 |
| Cushman & Wakefield | business, enterprise, public company | New York City | 1917 |
| CVS Health | organization, business, enterprise, public company | Rhode Island, Woonsocket | 1963 |
| CVS Pharmacy | business, pharmacy chain | Woonsocket | 1963 |
| Cypress Semiconductor | business | San Jose | 1982 |