- C.S. Francis & Co2
- C.S. Hammond & Company2
- C.T. Dearing Printing Co1
- CBS Television Network1
- CUE Art Foundation1
- CUNY-DCP Urban Research Group1
- Cabell, James Alston, 1852-19301
- Cahill, John T., 1903-1
- California Council of Civil Engineers and Land Surveyors1
- Call, William Timothy, 1856-19171
- Calumet Press1
- Cam, Gilbert Arthur, 1906-1
- Campbell, Helen, 1839-19182
- Campbell, N. H1
- Campbell, Robert Dale1
- Campbell, William W., 1806-18811
- Canada. Department of Trade and Commerce1
- Cane, Melville Henry1
- Canot, Pierre Charles, 1710-17772
- Cantine & Leake1
- Cantor, Jacob A. 1854-19211
- Cantrell, S1
- Canty, Samuel1
- Capek, Thomas, 1861-19501
- Capek, Thomas, 1895-1
- Carey, Hugh L1
- Carey, Mathew, 1760-18391
- Carleton, George Washington, 1832-19011
- Carman, Harry J. 1884-19641
- Carnegie Trust Company1
- Caro, Robert A1
- Carpenter, W. H. 1813-18991
- Carpenter, William, 1797-18741
- Carr, Joseph Bradford, 1828-18951
- Carroll & Cook1
- Carroll, Charles, 1876-19361
- Carroll, G. Danielson1
- Carroll, George D1
- Carruthers, Ralph Herbert, 1903-1
- Carstensen, Georg, 1812-18571
- Carter, Robert, pub., New York1
- Carteret Book Club1
- Carver, William1
- Carwitham, J1
- Casa Italiana Educational Bureau1
- Casa del Mar Club1
- Casey, T. L. 1831-18962
- Catella Jessurun, Jacob Spinoza, 1878-1
- Cathedral of St. John the Divine (New York, N.Y.)5
- Catherwood, Frederick1
- Catholic Church. Archdiocese of New York (N.Y.)1
- Catlin, George S1
- Catlin, George, 1796-18721
- Catskill Chamber of Commerce1
- Cavaglieri, Giorgio, 1911-20071
- Center for Community Change1
- Central Brooklyn Model Cities Housing Development Company1
- Central Debating League1
- Central Park Menagerie (New York, N.Y.)1
- Central Savings Bank (New York, N.Y.)1