Connecticut - Significance region: Local
| South Willington Historic District |
| Spanish House, The |
| Sprague, Elias, House |
| Springbank |
| Spring Grove Cemetery |
| Spring Hill Historic District |
| Stackpole, Moore, and Tryon Building |
| Stafford Springs Historic District |
| Stanton, Robert, House |
| Stapleton Building |
| Starr, C. J., Barn and Carriage House |
| Starr Mill |
| Sterling Homestead |
| Stevens, William, House |
| Stick Style House at Stony Creek |
| St. John's Episcopal Church |
| St. Mary's Parochial School |
| Stoddard, Capt. Mark, Farmstead |
| Stonington Cemetery |
| Stonington High School |
| St. Paul's Methodist Episcopal Church |
| Sts. Cyril and Methodius Church |
| Sturges-Wright House |
| Suburban Club |
| Sumner-Carpenter House |
| Swain-Harrison House |
| Swift, M. and Sons Company |
| Tariffville Historic District |
| Taylor's Corner |
| Telephone Exchange Building |
| Temple Beth Israel |
| Tephereth Israel Synagogue |
| Terry-Hayden House |
| The Lodges Historic District |
| Thompson, William H., Farmstead |
| Tiffany, Simon, House |
| Todd, Orrin, House |
| Torrington Fire Department Headquarters |
| Town Farms Inn |
| Town Hall |
| Town Hall and District School No. 6 |
| Treadway, Townsend G., House |
| Treadwell House |
| Tunxis Hose Firehouse |
| Turner, Dr. Philip, House |
| Turn-of-River Bridge |
| Umpawaug District School |
| Uncasville Mill Historic District |
| Union Church/St. Paul's Church |
| Union Depot |
| Union Green Historic District |
| Union School |
| Union Society of Phoenixville House |
| Union Station |
| Union Village Historic District |
| Unitarian Meetinghouse |
| United Bank Building |
| United Congregational Church |
| United Illuminating Company Building |
| United States Post Office, Westport, Connecticut |
| U.S. Post Office |
| US Post Office-Ansonia Main |
| US Post Office-Bridgeport Main |
| US Post Office-Greenwich Main |
| US Post Office-Manchester Main |
| US Post Office-Meriden Main |
| US Post Office-Milford Main |
| US Post Office-Naugatuck Main |
| US Post Office-New London Main |
| US Post Office-Norwich Main |
| US Post Office-South Norwalk Main |
| US Post Office-Stamford Main |
| Villa Bella Vista |
| Villa Friuli |
| Vine Street Apartment Buildings |
| Wallingford Railroad Station |
| Walnut Grove |
| Walnut Hill District |
| Waltersville School |
| Ward, William and Mary, House |
| Ward, William, Jr., House |
| Warner House |
| Warren Congregational Church |
| Warrenton Woolen Mill |
| Washington School |
| Washington Street School |
| Waterbury Brass Mill |
| Watkinson Juvenile Asylum and Farm School |
| Webb, David Jr. and Sarah, House |
| Webster, Horace, Farmhouse |
| Webster Memorial Building |
| Webster, Noah, Memorial Library |
| Webster School |
| Welch, David, House |
| Welles-Shipman-Ward House |
| West Boulevard Historic District |
| Westbrook Town Center Historic District |
| West End Commercial District |
| West End Congregation-Achavath Achim Synagogue |
| West End Historic District |
Data from United States Park Service and Wikidata
