| Alden Tavern Site | Lebanon | Site | 1998 |
| American Thermos Bottle Company Laurel Hill Plant | Norwich | District | 1989 |
| Ames, Winslow, House | New London | Building | 1995 |
| Anshei Israel Synagogue | Lisbon | Building | 1995 |
| Antone DeSant Houses | New London | Building | 2025 |
| Applewood Farm | Ledyard | Building | 1987 |
| Ashlawn | Sprague | Building | 1979 |
| Avery Homestead | Ledyard | Building | 1992 |
| Avery House | Griswold | Building | 1986 |
| Avery Point Lighthouse | Groton | Structure | 2002 |
| Avery, Thomas, House | East Lyme | Building | 1979 |
| Backus, Nathaniel, House | Norwich | Building | 1970 |
| Bacon Academy | Colchester | Building | 1982 |
| Baltic Historic District | Sprague | District | 1987 |
| Barns, Acors, House | New London | Building | 1976 |
| Bean Hill Historic District | Norwich | District | 1982 |
| Bennett Rockshelter | Old Lyme | Site | 1987 |
| Bill, Gurdon, Store | Ledyard | Building | 1982 |
| Blackledge River Railroad Bridge | Colchester | Structure | 1986 |
| Bozrah Congregational Church and Parsonage | Bozrah | Building | 1991 |
| Bradford-Huntington House | Norwichtown | Building | 1970 |
| Branford House | Groton | Building | 1984 |
| Brewster Homestead | Griswold | Building | 2000 |
| Bridge No. 1860 | Montville | Structure | 1993 |
| Broad Street School | Norwich | Building | 1984 |
| Buckingham, William A., House | Norwich | Building | 1982 |
| Bulkeley School | New London | Building | 1981 |
| Burnett's Corner Historic District | Groton | District | 1997 |
| Burnham Tavern | Lisbon | Building | 2022 |
| CHARLES W. MORGAN NHL | Mystic | Structure | 1966 |
| Carpenter House | Norwichtown | Building | 1970 |
| Carpenter, Joseph, Silversmith Shop | Norwichtown | Building | 1970 |
| Carroll Building | Norwich | Building | 1982 |
| Cedar Grove Cemetery | New London | District | 2024 |
| Central Vermont Railroad Pier | New London | Structure | 2005 |
| Champion, Henry, House | Colchester | Building | 1972 |
| Chapman, David, Farmstead | Ledyard | Building | 1992 |
| Charlton, Capt. Richard, House | Norwichtown | Building | 1970 |
| Chelsea Parade Historic District | Norwich | District | 1989 |
| Civic Institutions Historic District | New London | District | 1990 |
| Clark Homestead | Lebanon | Building | 1978 |
| Clark, Andrew, House | Lisbon | Building | 1979 |
| Cogswell, Edward, House | Griswold | Building | 1993 |
| Coit Street Historic District | New London | District | 1988 |
| Colchester Village Historic District | Colchester | District | 1994 |
| Commonwealth Works Site | Norwich | Site | 1998 |
| Converse House and Barn | Norwich | Building | 1970 |
| Cooper Site | Lyme | Site | 1987 |
| Deshon-Allyn House | New London | Building | 1970 |
| Downtown New London Historic District | New London | District | 1979 |
| Downtown New London Historic District (Boundary Increase) | New London | District | 1988 |
| Downtown Norwich Historic District | Norwich | District | 1985 |
| EMMA C. BERRY (Fishing Sloop) NHL | Mystic | Structure | 1994 |
| East District School | Norwich | Building | 1970 |
| Eastern Point Historic District | Groton | District | 1979 |
| Edward Bloom Silk Company Factory | New London | Building | 2021 |
| Eolia-Harkness Estate | Waterford | District | 1986 |
| Fanning, Capt. Thomas, Farmstead | Ledyard | Building | 1992 |
| Fish, Abel H., House | Salem | Building | 1982 |
| Fort Griswold | Groton | Building | 1970 |
| Fort Shantok NHL | Montville | Site | 1986 |
| Fort Trumbull | New London | Building | 1972 |
| Gales Ferry Historic District No. 1 | Gales Ferry | District | 1992 |
| Gales Ferry Historic District No. 2 | Ledyard | District | 2002 |
| Gorton, William, Farm | East Lyme | Building | 1984 |
| Graniteville Historic District | Waterford | District | 2003 |
| Greeneville Historic District | Norwich | District | 2005 |
| Griswold Point Historic District | Old Lyme | District | 2023 |
| Griswold, Florence, House and Museum NHL | Old Lyme | Building | 1993 |
| Groton Bank Historic District | Groton | District | 1983 |
| Hadlyme Ferry Historic District | Hadlyme | District | 1994 |
| Hallville Mill Historic District | Preston | District | 1996 |
| Hamburg Bridge Historic District | Lyme | District | 1983 |
| Hamburg Cove Site | Lyme | Site | 1987 |
| Harris, Jonathan Newton, House | New London | Building | 1982 |
| Hartford Colony | Waterford | District | 2005 |
| Hayward House | Colchester | Building | 1972 |
| Hempstead Historic District | New London | District | 1986 |
| Hempstead, Joshua, House | New London | Building | 1970 |
| Hempsted, Nathaniel, House | New London | Building | 1970 |
| Hodges Square Historic District | New London | District | 2017 |
| House at 130 Mohegan Avenue | New London | Building | 2009 |
| Huntington Street Baptist Church | New London | Building | 1982 |
| Huntington, Col. Joshua, House | Norwich | Building | 1972 |
| Huntington, Gen. Jedidiah, House | Norwichtown | Building | 1970 |
| Huntington, Gov. Samuel, House | Norwichtown | Building | 1970 |
| Jail Hill Historic District | Norwich | District | 1999 |
| Jordan Village Historic District | Waterford | District | 1990 |
| Kinne Cemetery | Griswold | Site | 2001 |
| L. A. DUNTON NHL | Mystic | Structure | 1993 |
| Lamb Homestead | Ledyard | Building | 1991 |
| Lathrop, Dr. Daniel, School | Norwichtown | Building | 1970 |
| Lathrop, Dr. Joshua, House | Norwichtown | Building | 1970 |
| Lathrop-Mathewson-Ross House | Lisbon | Building | 1982 |
| Laurel Hill Historic District | Norwich | District | 1987 |
| Lebanon Green Historic District | Lebanon | District | 1979 |
| Lee, Thomas, House | East Lyme | Building | 1970 |
| Leffingwell Inn | Norwichtown | Building | 1970 |
| Lester, Nathan, House | Ledyard | Building | 1972 |
| Lester, Timothy, Farmstead | Griswold | Building | 1998 |
| Lieutenant River III Site | Old Lyme | Site | 1987 |
| Lieutenant River IV Site | Old Lyme | Site | 1987 |
| Lieutenant River No. 2 | Old Lyme | Site | 1987 |
| Lighthouse Inn | New London | Building | 1996 |
| Little Plain Historic District | Norwich | District | 1970 |
| Little Plain Historic District (Boundary Increase) | Norwich | District | 1987 |
| Long Society Meetinghouse | Norwich | Building | 1976 |
| Lord Cove Site | Lyme | Site | 1987 |
| Lord, Capt. Enoch, House | Old Lyme | Building | 2007 |
| Lyman Viaduct | Colchester | Structure | 1986 |
| Main Sawmill | Ledyard | District | 1972 |
| Mashantucket Pequot Reservation NHL | Ledyard | District | 1986 |
| Mechanic Street Historic District | Stonington | District | 1988 |
| Merrill, James, House NHL | Stonington | Building | 2013 |
| Mill Brook Bridge | Lisbon | Structure | 1997 |
| Miner, Samuel, House | North Stonington | Building | 1976 |
| Montauk Avenue Historic District | New London | District | 1990 |
| Monte Cristo Cottage NHL | New London | Building | 1971 |
| Mystic Bank | Old Mystic | Building | 2014 |
| Mystic Bridge Historic District | Mystic | District | 1979 |
| Mystic River Historic District | West Mystic | District | 1979 |
| Natcon Site | Old Lyme | Site | 1987 |
| New England Hebrew Farmers of the Emanuel Society Synagogue and Creamery Site | Chesterfield | Site | 2012 |
| New London County Courthouse | New London | Building | 1970 |
| New London Customhouse | New London | Building | 1970 |
| New London Harbor Lighthouse | New London | Structure | 1990 |
| New London Ledge Lighthouse | New London | Structure | 1990 |
| New London Public Library | New London | Building | 1970 |
| New London Railroad Station | New London | Building | 1971 |
| Noank Historic District | Noank | District | 1979 |
| North Stonington Village Historic District | North Stonington | District | 1983 |
| Norwich Hospital District | Norwich-Preston | District | 1988 |
| Norwich Town Hall | Norwich | Building | 1983 |
| Norwichtown Historic District | Norwich | District | 1973 |
| Noyes, William, Farmstead | Ledyard | Building | 1992 |
| Occum Hydroelectric Plant and Dam | Norwich | Structure | 1996 |
| Ohev Sholem Synagogue | New London | Building | 1995 |
| Oil Mill Historic District | Waterford | District | 2023 |
| Old Lyme Historic District | Old Lyme | District | 1971 |
| Oswegatchie Historic District | Waterford | District | 2005 |
| Palmer, Capt. Nathaniel B., House NHL | Stonington | Building | 1996 |
| Palmer, John, House | Lisbon | Building | 2005 |
| Palmer, Luther, House | North Stonington | Building | 1979 |
| Park, William, House | Sprague | Building | 2007 |
| Peck Tavern | Old Lyme | Building | 1982 |
| Pequot Colony Historic District | New London | District | 1988 |
| Pequot Fort | Groton | Site | 1990 |
| Pequotsepos Manor | Mystic | Building | 1979 |
| Perkins-Bill House | Gales Ferry | Building | 2000 |
| Perkins-Rockwell House | Norwich | Building | 1985 |
| Plant, Morton Freeman, Hunting Lodge | East Lyme | Building | 1988 |
| Poquetanuck Village Historic District | Preston | District | 1996 |
| Post Hill Historic District | New London | District | 1993 |
| Preston City Historic District | Preston | District | 1987 |
| Prospect Street Historic District | New London | District | 1986 |
| Quaker Hill Historic District | Waterford | District | 2002 |
| Randall, John, House | North Stonington | Building | 1978 |
| Raymond-Bradford Homestead | Montville | Building | 1982 |
| River Road Stone Arch Railroad Bridge | Colchester | Structure | 1986 |
| Rocky Neck Pavilion | East Lyme | Building | 1986 |
| Rossie Velvet Mill Historic District | Stonington | District | 2007 |
| SABINO (steamer) NHL | Mystic | Structure | 1992 |
| Salem Historic District | Salem | District | 1980 |
| Selden Island Site | Lyme | Site | 1987 |
| Shaw Mansion | New London | Building | 1970 |
| Shepherd of the Sea Chapel | Groton | Building | 2025 |
| Slater Library and Fanning Annex | Griswold | Building | 2002 |
| Smith, Jabez, House | Groton | Building | 1981 |
| Smith, Samuel, House | East Lyme | Building | 1979 |
| Smith, Shubel, House | Ledyard | Building | 1996 |
| Springbank | Old Lyme | Site | 2001 |
| St. James' Episcopal Church | New London | Building | 2004 |
| Stanton, Robert, House | Stonington | Building | 1979 |
| Stoddard, Capt. Mark, Farmstead | Gales Ferry | Building | 1992 |
| Stonington Borough Historic District | Stonington | District | 1979 |
| Stonington Cemetery | Stonington | District | 2018 |
| Stonington Harbor Lighthouse | Stonington | Building | 1976 |
| Stonington High School | Stonington | Building | 1978 |
| Taftville | Norwich | District | 1978 |
| Telephone Exchange Building | Norwich | Building | 1983 |
| Thames Shipyard | New London | Building | 1975 |
| The Seaside | Waterford | Building | 1995 |
| Tiffany, Simon, House | Salem | Building | 1983 |
| Trumbull, John, Birthplace NHL | Lebanon | Building | 1966 |
| Turner, Dr. Philip, House | Norwichtown | Building | 1970 |
| U.S.S. NAUTILUS (submarine) NHL | Groton | Structure | 1979 |
| US Post Office-New London Main | New London | Building | 1986 |
| US Post Office-Norwich Main | Norwich | Building | 1986 |
| Uncasville Mill Historic District | Montville | District | 2021 |
| Uncasville School | Montville | Building | 2001 |
| United States Housing Corporation Historic District | New London | District | 1990 |
| Waldo, Edward, House | Scotland | Building | 1978 |
| Walnut Grove | Waterford | District | 2005 |
| War Office | Lebanon | Building | 1970 |
| Whale Oil Row | New London | District | 1970 |
| Wheeler Block | Colchester | Building | 1993 |
| Whitehall Mansion | Stonington | Building | 1979 |
| William Clark Company Thread Mill | Stonington | District | 2008 |
| Williams Memorial Institute | New London | Building | 1978 |
| Williams Memorial Park Historic District | New London | District | 1987 |
| Williams, William, House NHL | Lebanon | Building | 1971 |
| Wilson, John, House | Jewett | Building | 1985 |
| Winthrop Mill | New London | Building | 1982 |
| Woodbridge Farm | Salem | Building | 1997 |
| Woodward, Ashbel, House | Franklin | Building | 1992 |
| Woodworth, Nathan A., House | New London | Building | 1982 |
| Yantic Falls Historic District | Norwich | District | 1972 |
| Yantic Woolen Company Mill | Norwich | Building | 1996 |
| Yeomans, Edward, House | Groton | Building | 1978 |