Connecticut - Criteria: A (event)
| Sheffield Street Bridge |
| Shelton, William, House |
| Sherman, David, House |
| Sherman Historic District |
| Silvermine Center Historic District |
| Simeon North Factory Site |
| Simpson, Dr. Frank T., House |
| Simsbury Bank and Trust Company Building |
| Simsbury Railroad Depot |
| Sisson-South Whitney Historic District |
| Skee's Diner |
| Skilton Road Bridge |
| Slater Library and Fanning Annex |
| Sleeping Giant Tower |
| Smith, H. D., Company Building |
| Somers Historic District |
| Somersville Historic District |
| Sound Beach Railroad Station |
| Southbury Training School |
| South Congregational Church |
| South End Historic District |
| Southern New England Telephone Company Adminstrative Building |
| Southern New England Telephone Company Building |
| Southport Historic District |
| South School |
| Southwest District School |
| Southwest District School |
| Southwest Ledge Lighthouse |
| South Willington Historic District |
| Springbank |
| Stafford Hollow Historic District |
| Stamford Harbor Lighthouse |
| Stanley-Woodruff-Allen House |
| Stanton, Robert, House |
| Stapleton Building |
| Starr Mill Road Bridge |
| State Arsenal and Armory |
| State Park Supply Yard |
| Steamboat Dock Site |
| Steele, Allyn, House |
| Sterling Block-Bishop Arcade |
| Sterling Hill Historic District |
| Sterling Hill Historic District |
| Sterling Opera House |
| St. James' Episcopal Church |
| St. John's Episcopal Church |
| St. John's Episcopal Church |
| St. John's Protestant Episcopal Church |
| St. Luke's Episcopal Church |
| St. Mary's Parochial School |
| Stoddard, Capt. Mark, Farmstead |
| Stonington Cemetery |
| Stonington Harbor Lighthouse |
| Stonington High School |
| Stony Creek-Thimble Islands Historic District |
| Stony Hill School |
| Stratford Center Historic District |
| Stratford Point Lighthouse |
| Stratford Shoal Lighthouse |
| Strong House |
| Strouse, Adler Company Corset Factory |
| Sts. Cyril and Methodius Church |
| Suburban Club |
| Sunny Ridge Historic District |
| Swallen, James, House |
| Sweetland, Sophia, House |
| Swift, M. and Sons Company |
| System House |
| Taftville |
| Talcottville Historic District |
| Tatum, Corinne and George Liston Jr., House |
| Telephone Exchange Building |
| Temple Beth Israel |
| Temple Beth Israel |
| Terry-Hayden House |
| Terry's Plain Historic District |
| Terryville Waterwheel |
| Thames Shipyard |
| The Seaside |
| Thomaston Opera House |
| Thompson, William H., Farmstead |
| Todd, Orrin, House |
| Tolland County Courthouse |
| Tolland Green Historic District |
| Tongue Point Lighthouse |
| Town Bridge |
| Town Farms Inn |
| Tranquility Farm |
| Tully, William, House |
| Tunxis Forest Headquarters House |
| Tunxis Forest Ski Cabin |
| Tunxis Hose Firehouse |
| Turn-of-River Bridge |
| Tyler, John, House |
| Tyler, Solomon, House |
| Umpawaug District School |
| Uncasville School |
| Underwood Computing Machine Company Factory |
| Union Church/St. Paul's Church |
| Union Depot |
Data from United States Park Service and Wikidata
