Connecticut - Significance region: Local
| Old Town Hall |
| Old Town Hall |
| Old Westfield Cemetery |
| Old West Haven High School |
| Osbornedale |
| Oswegatchie Historic District |
| Palace and Majestic Theaters |
| Palmer, John, House |
| Palmer, Luther, House |
| Parker House |
| Parker-Hutchinson Farm |
| Parkville Historic District |
| Park, William, House |
| Parmelee House |
| Peck, Stow & Wilcox Factory |
| Peck Tavern |
| Pequotsepos Manor |
| Perkins-Bill House |
| Perkins, Maxwell E., House |
| Perkins-Rockwell House |
| Perry, David, House |
| Phelps, Capt. Elisha, House |
| Pike, Gustavus and Sarah T., House |
| Pine Grove Historic District |
| Pinney, David, House and Barn |
| Pinto, William, House |
| Plainfield Woolen Company Mill |
| Plant, Morton Freeman, Hunting Lodge |
| Plaster House |
| Platt, Col. Asa, House |
| Pledger, Jacob, House |
| Plumb House |
| Pomeroy, Arthur G., House |
| Pond-Weed House |
| Porter, Dr. J., House |
| Post, Augustus, House |
| Pratt, Dr. Ambrose, House |
| Pratt House |
| Pratt, Humphrey, Tavern |
| Pultz & Walkley Company |
| Putnam, Israel, Wolf Den |
| Quaker Hill Historic District |
| Ramsdell, Hezekiah S., Farm Site |
| Raymond-Bradford Homestead |
| Revolutionary War Campsite |
| Revonah Manor Historic District |
| Richardson, Nathaniel, House |
| Rider, John, House |
| Ridgebury Congregational Church |
| River Road-Mead Avenue Historic District |
| River Road Stone Arch Railroad Bridge |
| Riverside Cemetery |
| Riverton Historic District |
| Robbins, Unni II, House |
| Robinson, P., Fur Cutting Company |
| Rockwell Park |
| Root, Jonathan, House |
| Rowayton Depot Historic District |
| Rowe and Weed Houses |
| Royal Typewriter Company Building |
| Russell Company Upper Mill |
| Russell, Edward Augustus, House |
| Russell, Samuel Wadsworth, House |
| Sabbathday House |
| Sage-Kirby House |
| Saint Luke's Home for Destitute and Aged Women |
| Sanford-Curtis-Thurber House |
| Sanford, Frederick S., House |
| Sanford-Humphreys House |
| Sanseer Mill |
| Schlaraffia Burg |
| Schoverling, Carl F., Tobacco Warehouse |
| Scoville Powerhouse |
| Seaside Institute |
| Second Church of Christ |
| Sedgwick, Maj. Gen. John, House |
| Seelye, Seth, House |
| Seymour High School and Annex |
| Shambaugh House |
| Sharon Historic District |
| Shore Line Electric Railway Powerhouse |
| Short Beach Historic District |
| Sigourney Square District |
| Simsbury Bank and Trust Company Building |
| Simsbury Center Historic District |
| Simsbury Railroad Depot |
| Simsbury Townhouse |
| Skelton, Dr. Henry, House |
| Skinner, Jason, House |
| Sloper-Wesoly House |
| Smith, H. D., Company Building |
| Smith, Jabez, House |
| Smith, Samuel, House |
| Smith, Shubel, House |
| Sound Beach Railroad Station |
| Southington Public Library |
| Southport Railroad Stations |
| South School |
| Southwest District School |
| Southwest District School |
Data from United States Park Service and Wikidata
