Maine - Criteria: C (architecture/engineering)
| Stimson Memorial Hall |
| St. James Episcopal Church |
| St. John Catholic Church |
| St. John's Catholic Church |
| St. John's Episcopal Church |
| St. Joseph's Academy and Convent-Catherine McAuley School |
| St. Joseph's Catholic Church |
| St. Joseph's School |
| St. Lawrence Church |
| St. Mark's Episcopal Church |
| St. Mary's-By-The-Sea |
| St. Mary's Church |
| Stockton Springs Community Church |
| Stone Barn Farm |
| Stone, Capt. Nataniel, House |
| Stone, Elisha F., House |
| Stone House |
| Stone Schoolhouse |
| Stonington Opera House |
| Stover, Capt. Johnson H. Jr., House |
| St. Patrick's Catholic Church |
| St. Paul's Church and Rectory |
| St. Paul's Episcopal Church |
| St. Peter's By-The-Sea Protestant Episcopal Church |
| Strathglass Building |
| Strathglass Park District |
| Stroudwater Historic District |
| Sts. Peter and Paul Church |
| Sturgis and Haskell Building |
| Sturtevant Hall |
| Sunday River Bridge |
| Sunnycroft |
| Sunset Lodge |
| SURPRISE (schooner) |
| Swan Island Historic District |
| Swedish Lutheran Church |
| Symphony House |
| Talbot, James R., House |
| Tappan-Viles House |
| Tarr-Eaton House |
| Tarr, John, House |
| Temples Historic District |
| Temple, The |
| Tenants Harbor Light Station |
| Thacher-Goodale House |
| The Birches |
| Thomaston Historic District |
| Thompson Block |
| Thompson's Bridge |
| Thorndike, George, House |
| Tiffany Chapel |
| Tiffany, George S., Cottage |
| Tillson Farm Barn |
| Tillson, Gen. Davis, House |
| TIMBERWIND (Schooner) |
| Timmerhuset |
| Todd House |
| Topsham Fairgrounds Grandstand |
| Topsham Historic District |
| Topside |
| Tracy-Causer Block |
| Traip, Robert and Louisa, House |
| Tramway Historic District |
| Tranquility Grange No. 344 |
| Treat, Nathaniel, House |
| Trinity Episcopal Church |
| Troy Meeting House |
| Trufant Historic District |
| Tufts House |
| Turner Town House |
| Turrets, The |
| Two Cent Bridge |
| Ulmer, George, 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 |
| Unitarian Church of Houlton |
| United Baptist Church |
| Universalist Meeting House |
| Universalist-Unitarian Church |
| Upper Dallas School |
| U.S. Courthouse |
| U.S. Customhouse |
| U.S. Customhouse |
| U.S. Customhouse and Post Office |
Data from United States Park Service and Wikidata
