Connecticut - Area of significance: Industry
| Slater Library and Fanning Annex |
| Smith, H. D., Company Building |
| Somersville Historic District |
| South End Historic District |
| South Willington Historic District |
| Stafford Hollow Historic District |
| Stafford Springs Historic District |
| Starr Mill Road Bridge |
| Stony Creek-Thimble Islands Historic District |
| Stony Hill School |
| Strouse, Adler Company Corset Factory |
| Sweetland, Sophia, House |
| Swift, M. and Sons Company |
| Taftville |
| Talcottville Historic District |
| Tarrywile |
| Terry-Hayden House |
| Terryville Waterwheel |
| Thames Shipyard |
| Town Bridge |
| Uncasville Mill Historic District |
| Underwood Computing Machine Company Factory |
| Union Village Historic District |
| United Illuminating Company Building |
| Valley Falls Cotton Mill Site |
| Warrenton Woolen Mill |
| Washington Avenue Bridge |
| Waterbury Brass Mill |
| Waterbury Clock Company |
| West Goshen Historic District |
| West Granby Historic District |
| Westville Village Historic District |
| Whale Oil Row |
| Whitfield Cowles House |
| Whitney, Eli, Gun Factory |
| Wickham Road Historic District |
| Wilcox, Crittenden Mill |
| William Clark Company Thread Mill |
| Williams, J. B., Co. Historic District |
| Wilton Center Historic District |
| Winchester Repeating Arms Company Historic District |
| Winsted Hosiery Mill |
| Winthrop Mill |
| Wooster Sawmill and Gristmill Site |
| Yantic Falls Historic District |
| Yantic Woolen Company Mill |
Data from United States Park Service and Wikidata
