- Clark, Emmons, 1827-19051
- Clarke & Rapuano2
- Clarke, B. L1
- Clarke, Richard H. 1827-19111
- Clarkson, Matthew, 1758-18251
- Clay, Henry, 1777-18521
- Clayton & Kingsland1
- Clayton, John M. 1796-18561
- Cleaveland, N. 1796-18773
- Clews, Henry, 1836-19231
- Clifford B. Harmon & Co1
- Clinton, DeWitt, 1769-182810
- Clinton, DeWitt, 1805-18331
- Clinton, George, 1739-18121
- Clopper, Edward Nicholas, 1879-19531
- Clouston, Adella Octavia, 1864-1
- Clover Gardens (New York, N.Y.)1
- Club of Odd Volumes1
- Club of Printing House Craftsmen of New York1
- Clute, J. J1
- Co-operative Building Plan Association1
- Cochran, Edward A1
- Cochran, Edwin A1
- Cochrane, John, 1813-18981
- Cockrell, Francis Marion, 1834-19151
- Coffin, Frederick M1
- Cogswell, Joseph Green, 1786-18712
- Cohen, Benjamin A. 1896-19601
- Colden, Cadwallader D. 1769-18341
- Colden, Cadwallader, 1688-17761
- Coleman, Earle E1
- Coleman, Michael1
- Coler, Bird Sim, 1867-19411
- College of Physicians and Surgeons in the City of New York. Society of Alumni1
- Collegiate Reformed Protestant Dutch Church of the City of New York1
- Collier, Jeremy, 1650-17261
- Collins1
- Collins & Perkins1
- Collins, William Thomas, 1886-1
- Colonial Empire Marketing Board1
- Colonial Order of the Acorn. New York Chapter1
- Colton, G. Woolworth 1827-19011
- Colton, Julia M. 1848-1
- Columbia College (Columbia University)1
- Columbia College (New York, N.Y.)3
- Columbia College (New York, N.Y.). Committee on Site1
- Columbia University12
- Columbia University. College of Pharmacy1
- Columbia University. Institute of Arts and Sciences1
- Columbia University. Library1
- Columbia University. School of Architecture1
- Columbia University. Teachers College1
- Columbia University. Trustees1
- Commerce and Industry Association of New York. Committee on Water-Supply1
- Committee for Modern Zoning1
- Committee for Promoting the Royal Lancasterian System for the Education of the Poor1
- Committee of Fourteen (New York, N.Y.)1
- Committee of Seventy (New York, N.Y.)1
- Community Association of the East Harlem Triangle1
- Community Service Society of New York. Committee on Aging., Lower East Side Subcommittee1