Maine - Significance region: Local
| Stone Schoolhouse |
| Stonington Opera House |
| Stover, Capt. Johnson H. Jr., House |
| St. Patrick's Catholic Church |
| St. Paul's Church and Rectory |
| St. Peter's By-The-Sea Protestant Episcopal Church |
| Strand Theatre |
| Strathglass Building |
| Strathglass Park District |
| Stroudwater Historic District |
| Sturgis and Haskell Building |
| Summer Street Block |
| Sunday River Bridge |
| Sunnycroft |
| Sunset Lodge |
| SURPRISE (schooner) |
| Surry Town Hall |
| Surry Village School |
| Swedish Lutheran Church |
| Talbot, James R., House |
| Tappan-Viles House |
| Tarr-Eaton House |
| Temple Intervale School |
| Temple, The |
| Thatcher, Henry Knox, House |
| The Birches |
| """The Rim"" and Site of Fort Foster" |
| Thomas B. Reed School |
| Thomaston Historic District |
| Thompson Block |
| Thompson's Bridge |
| Thorndike, George, House |
| Tiffany Chapel |
| Tiffany, George S., Cottage |
| Tillson Farm Barn |
| Timber Point |
| Todd House |
| Tolman Cemetery |
| Topsham Fairgrounds Grandstand |
| Topsham Historic District |
| Topside |
| Town of Rumford Site |
| Tracy-Causer Block |
| Tranquility Grange No. 344 |
| Treat, Nathaniel, House |
| Trefethen-Evergreen Improvement Association |
| Trinity Episcopal Church |
| Troy Meeting House |
| Trufant Historic District |
| Tufts House |
| Turner Cattle Pound |
| Turner Town House |
| Turrets, The |
| Two Cent Bridge |
| Two Lights |
| Ulmer, George, House |
| Underwood, Joseph H., House |
| Union Block |
| Union Church |
| Union Church |
| Union Church |
| Union Church |
| Union Church |
| Union Church |
| Union Church, (former) |
| Union Church of Northeast Harbor |
| Union Church of Vinalhaven |
| Union Evangelical Church |
| Union Hall |
| Union Hall |
| Union Meeting House |
| Union Meeting House, (Appleton) |
| Union Meeting House, (Former) |
| Union School |
| Union School |
| Union Town House (Former) |
| Unitarian Church of Houlton |
| United Baptist Church |
| Universalist Meeting House |
| Universalist-Unitarian Church |
| Upper Dallas School |
| Upton Grange No. 404 (Former) |
| U.S. Courthouse |
| U.S. Customhouse |
| U.S. Customhouse |
| U.S. Customhouse and Post Office |
| U.S. Customhouse (Old Customhouse) and Post Office |
| U.S. Inspection Station-Calais (Ferry Point), Maine |
| U.S. Inspection Station-Coburn Gore, Maine |
| U.S. Inspection Station-Fort Fairfield, Maine |
| U.S. Inspection Station-Limestone, Maine |
| U.S. Inspection Station-Orient, Maine |
| U.S. Post Office |
| US Post Office-Bar Harbor Main |
| US Post Office-Camden Main |
| US Post Office-Lewiston Main |
| US Post Office-Old Town Main |
| US Post Office-Orono Main |
| US Post Office-Portland Main |
| US Post Office-Presque Isle Main |
Data from United States Park Service and Wikidata
