Correspondence to or from:
- Cadillac Motor Car Company, Detroit, Mich. (1926-1930)
- Cahill, Mortimer L., Chicago, Ill. (1921-1936)
- Calaghan & Company, Chicago, Ill. (1920)
- Calgary Herald, Calgary, Alta. (1933)
- California Dairyman, Los Angeles, Calif. (1923)
- California Fruit Growers Exchange, Los Angeles, Calif. (1929)
- California Guardsman, Sacramento, Calif. (1937-1939)
- California Petroleum Corporation, Los Angeles, Calif. (1927)
- California Southland, Pasadena, Calif. (1930)
- Call Bulletin, San Francisco, Calif. (1940)
- Call Home Magazine, San Francisco, Calif. (1930)
- Calthorp, Dion Clayton, London, England. (1924)
- Camden Daily Courier, Camden, N.J. (1904)
- Campbell, A.F., Delavan, Wis. (1936)
- Campbell Soup Company, Camden, N.J. (1929)
- Cameron, Edgar S., Chicago, Ill. (1919)
- Canada Lumberman, Toronto, Ont. (1930)
- Canadian Bookman, Toronto, Ont. (1924-1925)
- Canadian Business, Montreal, Que. (1940-1942)
- Canadian Customs Department, Ottawa, Ont. (1940)
- Canadian Forum, Toronto, Ont. (1924)
- Canadian Insurance, Toronto, Ont. (1920-1927)
- Canadian Messenger, Toronto, Ont. (1933-1940)
- Canadian Messenger of the Sacred Heart, Montreal, Que. (1931)
- Canadian Motorist, Toronto, Ont. (1927-1928)
- Canadian National Railways Magazine, Toronto, Ont. (1921)
- Canadian Newspaper Service, Ltd., Toronto, Ont. (1920)
- Canadian Popular Magazine, Sidney, N.S. (1931)
- Canadian Railway and Marine World, Toronto, Ont. (1931)
- Canadian Short Stories, Toronto, Ont. (1941)
- Canadian Stories, Deseronto, Ont. (1928)
- Cape Cod Ship Building Corp., Wareham, Mass. (1936)
- Capital Publishing Co., Bismarck, N.D. (1939)
- The Car, Philadelphia, Pa. (1932)
- Carbonator and Bottler, Atlanta, Ga. (1928)
- Cargo, Nashville, Tenn. (1937)
- Carillon, Montclair, N.J. (1934)
- Carlton, W.N.C., Chicago, Ill. (1914)
- Carneiro, A.M. & Company, New York, N.Y. (1938)
- Carolina Motorist, Greensboro, N.C. (1927-1931)
- The Carpenter, Indianapolis, Ind. (1928)
- Carpet & Rug World, New York, N.Y. (1928)
- Carroll, J.C., Chicago, Ill. (1924)
- Carroll Press, Inc., Columbus, Ohio. (1933)
- Carruth, Gordon, Waterbury, Conn. (1921)
- Carson, L.R. Inc., Crisfield, Md. (1935)
- Carson, Pirie Scott & Co., Chicago, Ill. (1936)
- Carteret Publications, New York, N.Y. (1942)
- Cartoons Magazine, Chicago, Ill. (1921)
- Carwood Publishing Co., New York, N.Y. (1927)
- Cary, Lucian, Westport, Conn. (1921)
- Case, B.E., Hartford, Conn. (1934-1935)
- Case, Robert Ormand, Portland, Or. (1934-1937)
- Case and Comment, Rochester, N.Y. (1928)
- Case Eagle, Racine, Wis. (1926-1937)
- The Casket, Antigonish, N.S. (1928)
- Cassell, Charles E., Chicago, Ill. (1923)
- Castle, Everett Rhodes, Cleveland, Ohio. (1937)
- Catching, Paul J., Middletown, Ohio. (1940)
- Caterpillar Tractor Co., San Leandro, Calif. (1928)
- Catholic Boy, Minneapolis, Minn. (1932-1942)
- Catholic Bulletin, St. Paul, Minn. (1924-1928)
- Catholic Citizen, Milwaukee, Wis. (1928-1930)
- Catholic Columbian, Columbus, Ohio. (1927)
- Catholic Girl, Belleville, Ill. (1941)
- Catholic Home, Oklahoma City, Okla. (1924)
- Catholic Mirror, Springfield, Mass. (1924-1925)
- Catholic Mutual Benefit Association, Montreal, Que. (1923)
- Catholic Northwest Progress, Seattle, Wash. (1931)
- Catholic Observer, Pittsburgh, Pa. (1925-1927)
- Catholic Press Union, Cleveland, Ohio. (1925-1927)
- Catholic Register & Canadian Extension Magazine, Toronto, Ont. (1931)
- Catholic Review, Baltimore, Md. (1927-1941)
- Catholic Transcript, Hartford, Conn. (1928)
- Catholic Union and Times, Buffalo, N.Y. (1935-1938)
- Catholic Vigil, Grand Rapids, Mich. (1924)
- Catholic Virginian, Richmond, Va. (1942)
- Catholic Women's World, Montroe, Mich. (1939)
- Caux, Len de, Washington, D.C. (1940)
- Caxton Club, Chicago, Ill. (1920)
- Caxton Printers, Ltd., Caldwell, Idaho. (1937-1938