- Clark, C. W. (Engineer)1
- Clason Map Co.3
- Cleland, Jane M.10
- Cleveland, H. W. S. (Horace William Shaler), 1814-19001
- Colby, Charles Galusha, 1830-1866?1
- Colton, J. H. (Joseph Hutchins), 1800-18931
- Columbia Planograph Co.1
- Comber, W. G.1
- Cook, R.1
- Cooley, George W.1
- Cooley, George W.(George Washington)1
- Cooley, George Washington (1845-1920)4
- Cox, William T. (William Thomas), 1878-19612
- Craddock, Campbell1
- Cram, George Franklin, 1841-19284
- Crosby, John Q. A1
- Curtice & Stateler.1
- Curtice, D. L. (David L.), 1828-19026
- Curtice, David L.3
- Curtiss Northwest Airplane Co.1