Connecticut - Criteria: C (architecture/engineering)
| Capewell Horse Nail Company |
| Capron-Phillips House |
| Captain Nathan Hale Monument |
| Cargill Falls Mill (Wilkinson Mill) |
| Carpenter House |
| Carroll Building |
| Carter, Hubbell, House |
| Case, Benomi, House |
| Case Brothers Historic District |
| Cassidy House |
| Castle, Dr. Andrew, House |
| Catlin, J. Howard, House |
| Cedar Hill Cemetery |
| Centerbrook Congregational Church |
| Center Burying Yard, Old |
| Center Street Cemetery |
| Central Avenue-Center Cemetery Historic District |
| Central Vermont Railroad Pier |
| Central Village Historic District |
| Chaffee, Hezekiah, House |
| Champion, Henry, House |
| Chandler, Capt. Seth, House |
| Chapel Street Historic District |
| Chapin, Philip, House |
| Chaplin Historic District |
| Chapman, David, Farmstead |
| Chapman, Taylor, House |
| Charlton, Capt. Richard, House |
| Charter Oak Bank Building |
| Charter Oak Firehouse |
| Chatfield Farmstead |
| Chelsea Parade Historic District |
| Cheney Building |
| Cheshire Historic District |
| Chevry Lomday Mishnayes Synagogue |
| Children's Village of the Hartford Orphan Asylum |
| Childs, Starling, Camp |
| Chivvis, Arthur and Lyn, House |
| Christ Church |
| Christ Church New Haven |
| Christ Episcopal Church and Tashua Burial Ground |
| Church Farm |
| Church of the Good Shepherd and Parish House |
| Church of the Holy Name |
| Church of the Holy Trinity and Rectory |
| City Hall-Monument District |
| Civic Institutions Historic District |
| Clark, Andrew, House |
| Clark, Avery, House |
| Clark Brothers Factory No. 2 |
| Clark, Capt. John, House |
| Clark Farm Tenant House Site |
| Clark Homestead |
| Clay Hill Historic District |
| Clinton Village Historic District |
| Coffing, John C., House |
| Cogswell, Edward, House |
| Coite-Hubbard House |
| Coit Street Historic District |
| Colchester Village Historic District |
| Colebrook Center Historic District |
| Colebrook Store |
| Collins and Townley Streets District |
| Collinsville Historic District |
| Colony Street-West Main Street Historic District |
| Colt Industrial District |
| Colt, James B., House |
| Colton, Benjamin, House |
| Columbia Green Historic District |
| Commercial Trust Company Building |
| Commodore Hull School |
| Commonwealth Works Site |
| Compo-Owenoke Historic District |
| Comstock, Abijah, House |
| Comstock-Cheney Hall |
| Comstock's Bridge |
| Cone, Jared, House |
| Congregational Church of Plainville |
| Congress Street |
| Connecticut General Hospital for the Insane |
| Connecticut General Life Insurance Company Headquarters |
| Connecticut Hall, Yale University |
| Connecticut Railway and Lighting Company Car Barn |
| Connecticut State Capitol |
| Connecticut Statehouse |
| Connecticut State Library and Supreme Court Building |
| Connecticut Valley Hospital Cemetery |
| Converse House and Barn |
| Cook, John, House |
| Copper Ledges and Chimney Crest |
| Cos Cob Power Station |
| Cos Cob Railroad Station |
| Cosier-Murphy House |
| Cossitt, Frederick H., Library |
| Coult, Abraham, House |
| Cove Island Houses |
| Coventry Glass Factory Historic District |
| Cowles, Capt. Josiah, House |
| Cowles, Gen. George, House |
| Crandall, Prudence, House |
Data from United States Park Service and Wikidata
